Hi
Iv seen this a couple times and this issue really show how fragile LCD displays are
I think your display has been internaly damaged ,not cracked but damaged
I’m order to confirm this I would try unplugging the the display and reconnect it and see if the issue persists
Also try bleeding the battery down till dead as iv had this issue with iPods having battery static after having them unplugged or replaced
Hopefully this helps
Thanks:-)