Notification keeps popping up after texting

Hello,

I have a strange problem with an ONE PLUS 5, last week i changed the display of the one plus5 and all seems to work properly,

Now the client came back and he told me that when he opend excel the phone gets his own life (like ghosting , notifcation bar keeps poppin up when texting a message.)

When he reboots the phone , the phone works like normal and has no problems at all.

i told him to reinstall the app and see what happens..

Same thing,

I am worried that i might damaged something on the motherboard… or is this a faulty touch screen, but the weird thing is that when he restarts the phone and dont open the APP EXCEL then everthing is fine…

i hope someone can help me with this kind of problem.