iPhone SE turning itself off on lock screen?

Phone was dropped down the toilet. I tried to fix it using the isopropyl alcohol method. All seemed fine, but then the phone turns itself off when it's on the lock screen every time.

What's happening here? Is it the battery? (As it was replaced due to me ruining the original when I tried to remove it) is it the screen itself??

Also, which areas do I need to check to try and figure out what's happened.