Intermittent grayed out WiFi and boot-loop

Hey guys

So I recently bought a cracked iPhone 8 with the intention of fixing it and flipping it. When I checked it out before buying, everything worked 100% fine. I’d say 1 out of every 8 reboots it will hang for a good 10 minutes on the apple logo. Sometimes after hanging there for a while it will boot up just fine like nothing ever happened. Sometimes it will hang indefinitely until the battery dies or it it iTunes restored. A simple hard reboot will not do it. The most common case is it will hang for a bit, boot and have grayed out WiFi until the phone has been rebooted. I’ve never seen it have grayed out WiFi without it hanging on the Apple logo. Upon further inspection, i’ve found the phone has some water damage. I sent the board out to a company (Along with a Audio IC iPhone 7), but they didn’t do anything to either phone aside break the 7 and send them back. The board doesn’t appear to have any visible corrosion, but there’s some by the Camera in the frame. I’m wondering what I should check to try and get this phone up and running normally again. Any and all responses appreciated. Thanks :)