Have you tried contacting TCL support yet to inquire further? I'd suggest starting there to see what options or suggestions they can provide. Each Roku TV manufacturer provides direct support for their products running the Roku OS.
I too am having the issue of the Sling app constantly wanting to be turned on. I don't have a subscription to Sling, either. I can't get through much of a show without being interrupted non-stop from it going over to Sling. Why is this occurring?