Got one (TCL 49S405) with exactly same failure. Traced it to at least the COF flex to the panel on both sides so can't cut one side and depend on the other. Details here (post #5 in the thread. Post #1 is detail explanation of symptom)
https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-tvs-and-video-sources/3666063-tcl-49s405-double-image?p=3666203#post3666203