I am sorry to hear that you are experiencing this issue.
In order to help you best we will need some more information:
1) What version of Visual Studio and Test Studio you are using?
2) Could you please send us the application log
when this problem happens. Clear it first and then reproduce the issue.
3) If this issue happens only with a specific project, could you please send us the project. If the project is very large, you can also use Dropbox or Google Drive. Please upload the project folder, then share the folder and paste a link in this forum thread.
Looking forward to hearing from you.