Something changed recently, and unfortunately, I can make the PIP move from the upper right (where it should be) to the middle left, covering 1/4 of the guide on FireTV. I hope this is not a feature.
All I have to do is start channels, use PIP (it is in correct location), browse to some other channel, use PIP again and then it launches over the guide
It will keep launching in the bad position until I restart channels, and then the process starts over.
I just realized, one thing that changed recently, is that I moved from a FireTV 4k to a FireTV 4k Max. I don't remember if the problem existed with the 4k.