If it were a bad LED strip, then it wouldn't cause the TV to reboot. So that likely is not the problem.

I just wanted to take a moment to point out, this is not repairing. Despite what most 'so-called' repair shops do these days, swapping boards until you get a product working again is not repairing. Any high school kid can do board swaps.

To actually repair a product would start with getting a schematic. Then testing circuits on the board, finding problems, and tracing it back to the source of the issue. This is especially useful when you may have a problem on another board, that is damaging a 2nd board. You swap one board, get it working for a little while and then that board gets damaged - because you never troubleshooted why the board failed to begin with.

This among many other reasons is why the fight for "Right-to-repair" is so important. It affects everyone's life whether directly or indirectly.