I haven't experienced the same exact issue but I've had endless problems with the combination of a TCL 65R635 tv and an Alto 9+ soundbar. Audio sync issues, soundbar refuses to download software update, soundbar causes Apple TV 4K to freeze and show a black screen, etc... TCL sent me 4 replacement soundbars and the 4th one has more or less worked but in the middle of it all I got fed up and bought an LG soundbar for the 65R635 and it has solved all of those problems.
I was past the return period for the Alto 9+ so I hooked up the 4th one they sent me to a TCL 43" series 4 TV which I use as my computer monitor and second TV. It also has issues with the audio sync and once in a while starts making static noises and seems to lose the audio signal from the TV. The only way to fix that is to disconnect the HDMI cable from the TV's arc port, go into the TV settings and remove that port, then reconnect the soundbar.
The Alto 9+ is a piece of junk, imo. It doesn't even have a menu that tells you what format audio it is receiving or playing. The TCL Roku TVs aren't much better. They do have a good picture compared to other TVs in the same price range but they have all kinds of software problems, audio sync issues, etc...
I don't plan on buying a new TV for at least several years but when it's time to replace my 65R635, it will not be with another TCL, nor will I ever buy another TCL soundbar.
Good luck with yours. If you can return the soundbars, you may want to consider doing that.