URL: https://m.youtube.com/watch?v=bD6sTDH9Zdc

Browser / Version: Firefox Mobile 65.0
Operating System: Android 8.0.0
Tested Another Browser: Yes

Problem type: Something else
Description: pip on yt playlist with autoplay does not back fullscreen
Steps to Reproduce:
play yt playlist leaving autoplay on
enter pip mode
wait until video of Florence and the machine finish and yt start playback next one

it does not back to pip mode as full screen, or it does in own way

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