Thank you for contacting Telerik support. We are glad that you have been able to find a workaround.
Another viable workaround, should you find the simulator becoming corrupted again is to clear the AppBuilder cache. After you have closed the simulator and the extension, you can go to %localappdata%\Telerik\BlackDragon
and remove the Cache
folder. This should cause the simulator, on next start, to reset and repair itself.
Usually, the reported behavior occurs when you run the VS extension and the Windows client simultaneously, or when a process locks one or more files in your project.
We would appreciate any additional details about the original project, setup and situation with which you observed the issue, as this might help us identify the culprit and reduce the occurrence of such issues in the future.