Reproduction steps:
1. Open the user's attached "FocusSwitch-A.zip" and "FocusSwitch-B.zip" projects side-by-side
2. Load the "SampleScene" in each project
3. Enter Play mode in the "FocusSwitch-A"
4. Observe the HMD view ("FocusSwitch-A" project's Game view is rendered)
5. Enter Play mode in the "FocusSwitch-B"
6. Observe the HMD view

Expected result: the "FocusSwitch-B" project's Game view is rendered
Actual result: a black screen is rendered (see the attached "repro.mp4")

Reproducible with XR SDK: 3.2.13, 4.0.3 (2019.4.26f1, 2020.3.8f1, 2021.1.6f1, 2021.2.0a16)
Could not test with 2018.4 (no XR SDK available)

Notes:
- the issue is not reproducible with Legacy XR
- sometimes the "FocusSwitch-A" project's view stays rendered instead of a black screen
- switching the focus back to the first project and waiting a few seconds (~3-5s) resolves the issue (see "fix.mp4" video)

Tested with:
- Oculus Rift