If the user makes a project where the modules tab appears in Tools > Debug and then reboots the project, the modules tab disappears. This only happens if the project that is loaded has the module tab present.
Error message from the logs show the following:
1. Create a VR template
2. Ensure the modules tab is listed in Tools > Debug
3. Close the engine
4. Reload the VR template
Expected Result: Modules tab consistently loads
Actual Result: Modules tab fails to load
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-149585 in the post.