Steps to reproduce:
You can switch to portrait mode after re-opening the app.
The video is stuck in landscape mode after re-opening the app.
65 is going to release in a couple of weeks and this isn't a blocker for the release. Marking wontfix for 65.
Since it's working in 66 I'm closing this bug as WORKSFORME.
I can reproduce this issue on the latest version of Beta 66.0b3 and Release 65.0 build 2 using:
Due to that, I'll reopen the issue.
This issue is still reproducible on Beta 68.0b5 using Samsung Galaxy Note 8 (Android 9).