Actually, the towel trick is really bad for the console... it just bakes the board even more. You got lucky it worked at all. That method warps the motherboard over time. Replacing the thermal paste was the right move, but the real fix needs more. The GPU heat sink needs new thermal pads too, and you have to make sure the X-clamps aren't putting uneven pressure. Might want to look up the bolt mod fix if it happens again.