I experienced this several times now:
I have all patch windows closed (really closed, not by middle-click), but renderers are still open and running (camera and OpenCV detection in this case were still active).
This time, I had the impression editing the patch was not reacting anymore (changes in skia-io-boxes without effect) before closing, which was why I decided to close the patch. After closing vvvv and reopening, everything back to normal.
[2021.4.8 stable] on Intel NUC i5 without dedicated Graphics Card (only Intel Iris onboard).