Black screen because of shield between two console parts

Hi everyone, I’ve hacked switch lite with PicoFly. But when I built it back there was black screen, but sound after short scheen flash.
I found out that’s of shield between two console motherboards and inserted it a bit harder, but after a few days I had absolutey the same problem. I put it hard again. Everything worked for a week, it just layed in by desk a few days, finaly shork flash and black screen back. I restarted it a few times and screen worked again.
Does shield is blame or there may be something else? Played for a 15 minutes and everything working fine.