The new PIP is a huge improvement over the old and after a lot of testing, I’ve only come across one intermittent issue where maximizing the PIP window will cause the playing video to simply disappear. I can’t find a repeatable pattern to duplicate this issue…
What button is it that you're hitting when this happens?
I used the maximize button in the upper right corner of the PIP window.
After much testing, I can confirm that this issue (video disappears after maximizing from PIP) occurs in the following situation:
Starting a video from a deep link sometimes fails to play the video and instead only opens the video description card (not sure what it’s called). Playing any video after this whether using a deep link or manually selecting a video and going from PIP to full screen will always cause the video to disappear.
I should note that I’m referring to iPadOS and cannot confirm the same behavior on iOS.