Strange Dolby/+ issue on TCL 6 series

A very similar thing is happening to me -- I just now joined to post about it. I also have a TCL 6, and mine is connected to a Sony STR-DH590 receiver. I have a 5.1 setup in our living room, and I like to use the receiver's Pro Logic II setting to upmix stereo signal (in shows/movies that don't encode 5.1) to play through my surround speakers. The only way I can get the PLII mode to work is to use either the TCL's Auto Passthrough or PCM-Stereo settings. I prefer passthrough so my receiver can decode DD+ signal when it's available. But same as you, whenever I rewind of fast-forward (in Netflix, Amazon, etc), my receiver loses the DD+ signal and instead shows that it's receiving Linear PCM. There's also a very noticable jump up in volume. If I restart the program, it goes back to DD+

I'd really like to find a solution that would allow me to use passthrough without having the TV lose the DD+ signal every time I rewind. For now, I'm just keeping it on PCM-Stereo and letting my receiver's PLII setting do its thing, but that's far from ideal.