Test cases shouldn't be added to a complete test suite and when a Query Based Suite is marked as complete the query continues to run and more test cases are being added to the suite. TFS needs to stop running the query for query based suites when they are marked as complete, or prevent test cases from adding to a completed test suite (Query or Static).
Icons not visible on TFS2017.1/RC2
TFS 2017.1 notification management ERROR
Cannot add TFS server group to Access Level
Licence Using at TFS 2017 Report