PiP doew not work on madOS 2.1.2 on Vernee Thor with YouTube

I have installed madOS on my Vernee Thor. The PiP (Picuter-in-picture) is a good news, but it doesn't work with YouTube (it works with Google Maps an Chrome). My device: Vernee Thor, I have installed Android 8.1.0 (madOS), before I had Android 7.0. I wiped when installing. The bug existed from the beginning.