I'm sorry you're having this experience. Roku's position is: if the "how to" self-support page doesn't fix it, then you have a hardware issue. They're making it clear. It's not anything they're going to fix. The disturbing thing about this is that TCL is their licensed partner. You'd think after hundreds of reports of this problem, there would be some kind of cooperation between licensor, licensee & the person who bought their respective wares. But, instead, each new report is treated like "we've never heard of this before. Please read this page, then talk to *your* tv maker. Keep us informed. (moi! <toodles>)."
It speaks volumes, doesn't it?
I'd be thinking about retail sites (reviews on every Roku TV found).
I have no idea if this problem is due to hardware, or Roku's obviously sloppy envelopment. We've seen enough 9.4 breakage to believe this problem must be related. (The proverbial "boy who cried wolf" defaults to that view.). But, maybe it's a problem with Roku's partner. Whatever it is: it's undeniable by now. But, Roku is absolutely no help. They're not having an honest conversation with you. If TCL is abusing all you people, Roku is just as guilty by acting like nothing's happening. They must know what's going on by now. It must feel insulting to see such cavalier disingenuous. ("We know even less about it than you do.").
"People are often amazed at how much we’ve done with the number of engineers we’ve got." (Roku CEO Anthony Wood, Austin Statesman, Oct 4, 2019). "Amazed" is one way of putting it.