I have run into the same problem, BUT a superbug version where switching to a new USB stick did not rectify it. I have factory reset the tv and did so before inserting a brand new USB straight from the package. It still won’t record properly and blanks out every few seconds until I removed the drive.
I would believe it is a pvr issue where the tv is not handling the writing to the USB drive properly.
I have contacted support, but will return the tv as it is only 2 months old
My TCL 55" went through 4 USB flash drives in less than 12 months and unit is still under warranty. After several emails with TCL support they sent a technician to replace the main board. Took about 15 minutes to make repairs. I will do a follow up after a few months to see if problem is fixed.