When the issue has occurred bellow two event log items are also generated:

Log Name: Application
Source: .NET Runtime
Date: 6/19/2018 11:29:15 AM
Event ID: 1023
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: xxxxxx
Description:
Application: devenv.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an internal error in the .NET Runtime at IP 734B7A88 (73400000) with exit code 80131506. Event Xml:
<Event xmlns="https://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name=".NET Runtime" />
<EventID Qualifiers="0">1023</EventID>
<Level>2</Level>
<Task>0</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2018-06-19T09:29:15.476480200Z" />
<EventRecordID>6609</EventRecordID>
<Channel>Application</Channel>
<Computer>xxxxxxx</Computer>
<Security />
</System>
<EventData>
<Data>Application: devenv.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an internal error in the .NET Runtime at IP 734B7A88 (73400000) with exit code 80131506.
</Data>
</EventData>
</Event>

Log Name: Application
Source: Application Error
Date: 6/19/2018 11:29:16 AM
Event ID: 1000
Task Category: (100)
Level: Error
Keywords: Classic
User: N/A
Computer: xxxxxxxxxxxx
Description:
Faulting application name: devenv.exe, version: 15.7.27703.2035, time stamp: 0x5b232892
Faulting module name: clr.dll, version: 4.7.3110.0, time stamp: 0x5ae8c35b
Exception code: 0xc0000005
Fault offset: 0x000b7a88
Faulting process id: 0x2d108
Faulting application start time: 0x01d407af4c9d87f3
Faulting application path: C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\devenv.exe
Faulting module path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
Report Id: 30eb3f4f-ccd6-4b43-8749-6c99a803ee69
Faulting package full name:
Faulting package-relative application ID:
Event Xml:
<Event xmlns="https://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Application Error" />
<EventID Qualifiers="0">1000</EventID>
<Level>2</Level>
<Task>100</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2018-06-19T09:29:16.935254900Z" />
<EventRecordID>6610</EventRecordID>
<Channel>Application</Channel>
<Computer>xxxxxxxxxxxxx</Computer>
<Security />
</System>
<EventData>
<Data>devenv.exe</Data>
<Data>15.7.27703.2035</Data>
<Data>5b232892</Data>
<Data>clr.dll</Data>
<Data>4.7.3110.0</Data>
<Data>5ae8c35b</Data>
<Data>c0000005</Data>
<Data>000b7a88</Data>
<Data>2d108</Data>
<Data>01d407af4c9d87f3</Data>
<Data>C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\devenv.exe</Data>
<Data>C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll</Data>
<Data>30eb3f4f-ccd6-4b43-8749-6c99a803ee69</Data>
<Data>
</Data>
<Data>
</Data>
</EventData>
</Event>

This issue has also occurred when NuGet packages were tried to add.

After I install "Tools for NuGet by Base16.net" addon visual studio works without the crash.

in the log of the tool, I have:

2018-06-22 08:36:45 - The project 'yyyyyy' has an invalid reference to 'System.Collections', file not found ('')
2018-06-22 08:36:45 - The project 'yyyyyy' has an invalid reference to 'Microsoft.CSharp', file not found ('')

In the properties of the reference, it is resolved to

C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\Microsoft.NET.Build.Extensions\net461\lib\System.Collections.dll and

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.6.2\Microsoft.CSharp.dll

It seems that some references not resolved unique, forr example

c:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\CoreCon\Binaries\Phone Tools\Debugger\CoreClr\x64\Microsoft.CSharp.dll 439,744 05/24/2018 21:46 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.7.1\Microsoft.CSharp.dll 47,784 10/04/2017 01:21 -a--
c:\Program Files (x86)\MSBuild\15.0.Net.NetNative\15.0.24211\arm\ilc\lib\IL\Microsoft.CSharp.dll 451,272 02/13/2017 16:54 -a--
c:\Program Files (x86)\MSBuild\15.0.Net.NetNative\15.0.24211\x64\ilc\lib\IL\Microsoft.CSharp.dll 451,272 02/13/2017 16:52 -a--
c:\Program Files (x86)\MSBuild\15.0.Net.NetNative\15.0.24211\x86\ilc\lib\IL\Microsoft.CSharp.dll 451,272 02/13/2017 16:52 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.7\Microsoft.CSharp.dll 47,808 02/08/2017 22:56 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.6.2\Microsoft.CSharp.dll 47,304 07/14/2016 14:43 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.6.1\Microsoft.CSharp.dll 47,296 11/05/2015 19:36 -a--
c:\Program Files (x86)\Common Files\microsoft shared\Phone Tools\12.0\Debugger\target\x86\Microsoft.CSharp.dll 439,816 10/29/2015 22:28 -a--
c:\Program Files (x86)\Common Files\microsoft shared\Phone Tools\12.0\Debugger\target\armv4i\Microsoft.CSharp.dll 439,816 10/29/2015 22:24 -a--
c:\Program Files (x86)\Common Files\microsoft shared\Phone Tools\12.0\Debugger\target\x64\Microsoft.CSharp.dll 439,816 10/29/2015 22:24 -a--
c:\Program Files (x86)\Microsoft SDKs\NuGetPackages\Microsoft.CSharp\4.0.0\lib\dotnet\Microsoft.CSharp.dll 451,272 07/22/2015 22:06 -a--
c:\Program Files (x86)\Microsoft SDKs\NuGetPackages\Microsoft.CSharp\4.0.0\lib\netcore50\Microsoft.CSharp.dll 451,272 07/22/2015 22:06 -a--
c:\Program Files (x86)\Microsoft SDKs\NuGetPackages\Microsoft.CSharp\4.0.0\ref\dotnet\Microsoft.CSharp.dll 22,480 07/22/2015 22:06 -a--
c:\Program Files (x86)\Microsoft SDKs\NuGetPackages\Microsoft.CSharp\4.0.0\ref\netcore50\Microsoft.CSharp.dll 22,480 07/22/2015 22:06 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.6\Microsoft.CSharp.dll 48,320 06/19/2015 23:14 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile111\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile259\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile49\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile7\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile75\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.5\Profile\Profile78\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile151\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile157\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile31\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile32\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile44\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.6\Profile\Profile84\Microsoft.CSharp.dll 22,480 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile154\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile158\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile23\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile24\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile255\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile344\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile46\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETPortable\v4.0\Profile\Profile47\Microsoft.CSharp.dll 22,640 03/02/2015 10:54 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.5.2\Microsoft.CSharp.dll 49,344 05/28/2014 04:35 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.5.1\Microsoft.CSharp.dll 49,264 08/13/2013 00:19 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETCore\v4.5\Microsoft.CSharp.dll 22,528 09/26/2012 03:16 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.5\Microsoft.CSharp.dll 49,168 09/26/2012 03:16 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.0\Microsoft.CSharp.dll 65,376 03/18/2010 18:31 -a--
c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.0\Profile\Client\Microsoft.CSharp.dll 65,376 03/18/2010 18:31 -a--

and also exists in the GAC

c:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--
c:\Windows\WinSxS\x86_netfx4-microsoft.csharp_b03f5f7f11d50a3a_4.0.15671.0_none_0e4b3abea03268c3\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--
c:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.CSharp\v4.0_4.0.0.0__b03f5f7f11d50a3a\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--
c:\Windows\WinSxS\msil_microsoft.csharp_b03f5f7f11d50a3a_4.0.15671.0_none_de66ef8cba8ebe5a\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--
c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--
c:\Windows\WinSxS\amd64_netfx4-microsoft.csharp_b03f5f7f11d50a3a_4.0.15671.0_none_c69e03e78bb63fbd\Microsoft.CSharp.dll 486,488 04/12/2018 01:35 -a--

I hope that above information will help to figure out what happening.

If you need any particular log file (if exists) or you have some scenario which I can try, please let me know.