iPhone 6 acts weird, I suspect waterdamage

Hi all,

My mother had a iPhone 6 with shattered glass. She upgraded, and i decided to replace the screen. I have done this one time before on this phone. I do iphone repair as hobby, and i have been doing it for a few years now.

Lets get to the point. I replaced the screen, and after a little time of use the wifi and bluetooth suddently went dead. The wifi button is greyed out. (I have experienced this many times on iphone 4s) Anyways, i took apart the phone, and used a heat gun on the wifi chip, but without luck. I've tried all sort of things, and i am sure it is not a software problem.

Then, after laying it down for a while. I had a look on it again today. This phone is acting very strange now, because the clock dosn't go forward. The timezone wont set, eventhough it works with cellular data. This happened many times before when i disconnect the battery, but it usually fixes itself after connecting to the web.

On the top corner i can see som small traces of water. But nothing big. And i cant really think of any other solution to this than waterdamage. But the strange this is that it all stopped working after i replaced the screen.

I don't feel like the phone has any value, i wanted to sell it, but it isn't worth much now. Is there anything i can do to fix it, or is this phone dead?

Greetings from Norway, thank you in advice!