I can't really follow, does it works at 4.8 regardless if with or without media_build ? If yes then it is likely a usb problem (maybe something different) and has nothing to do with the dvb drivers. Of course it opens a gigantic field of possibilities ;D I try to find something suspicious. Btw I try to do you a 4.10 build maybe it is already fixed there and we can backport it.
It worked without media_build. I haven't repeated the recording playback test after getting the media_build version.
I'll try to test the 4.10 build in the evening. I hope I find the time to do it today.