This is the all well too known glitchy display issue. You normally cannot see the glue going bad visually other than the displays not working. You need to repair them and preferably not with any heat trick, only soldering is a proven long term solution.
Just had a pair of displays for repair a few days ago where one cable was completely detached due to the oven trick. I got it repaired this time, but it is harder to do and when it fails, it is as good as irreparable.