iPhone turns off when lock phone. Water Damage.

I accidentally sent my phone for a cycle in the washing machine, I left it to dry for a few days and then when the phone would not power past the initial white logo screen I ordered a new battery and replaced this. The phone is now fully operational when connected to the computer or mains via the charging cable, or when the screen is not turned off or the phone locked. When the phone is locked and not plugged in, the home and power buttons work on opening up the phone again for about a minute and then the phone will not power back on unless it is reconnected with the charging cable. The phone does not turn itself off randomly if it is connected via cable even when locked.

I have left the phone unlocked until the battery got down to 0%, tried a soft reset, a full reset via iTunes and this issue will not go away. Is this something I can fix by replacing a part inside the phone or is there a software fix?

Thank you