New charging flex still restarts every 3 mins

When I was on holiday my iPhone got wet which let to the phone screen being blank when the phone was still making sounds. When I got home I replaced the screen and battery which fixed that problem but then it started restarting every 3 minutes.

The crash log said Prs0 /nservice backboardd, so I really this was linked to the charging flex cable. I replaced the cable only to find the issue still being present. I decided to purchase an entire new casing with an authentic charge flex cable, battery etc all I need to do was place my motherboard and screen. So I've just done that but still the phone restarts every 3 mins and the same error log. I have come to the conclusion that there must be water damage on the motherboard? If this is the case is there any way I can fix it like cleaning with a cotton bud and alcohol?

Thanks