As of the latest TestFlight beta there is a new PIP implementation that can be enabled that will hopefully provide a better experience.
To enable it, download the latest Testflight beta and then go to Settings -> Debug and enable Use Experimental PIP.
The new implementation will make it possible to seek forward and backward when watching Live TV and should generally be a more reliable experienc.
This change does not impact tvOS.
Please try it out and let us know how it works for you.
The latest TestFlight beta has improvements around the integration with the playback controls in Notification Center.
I’ve been testing the new experimental PIP since it was released and it’s awesome! It works SO much better than the previous version and I can now use it reliably. Thank you so much for your hard work as I greatly appreciate it! 
The new PIP has been made the default and the old one is available in the Debug menu. There should be no need to use the old one unless instructed by a developer while diagnosing an issue.