Beer Damage - Power Button Not Working (But phone works)

I would replace the Power Button Flex by following this guide. However, the problem may be logic board related but the only way you will know for certain is by trying a replacement part first.

It must be said however that the “bag of rice solution” is not a solution at all. All it does is allow the liquid to dry. Depending on the quantity and the type of liquid, as well as it’s location within the phone, may cause little to extensive damage to the logic board when it evaporates and leaves behind mineral (and in your case sugar) deposits which can cause corrosion. The fact is that you have some random shutdowns and these were most likely caused by the beer. IMHO, when you have the phone open to replace the PB flex, I would also remove the logic board and try to clean it as much as possible following these directives:

• Open your phone and remove the logic board (follow the same guide as above)
• Inspect the logic board, especially around the connectors and look for corrosion.
• Inspect both sides of the board. Unfortunately, most of the board is covered in shields. That's usually where the damage is occurring.
• Put your board in a container with >90% isopropyl alcohol and let it sit for a while.
• Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.
• Rinse in alcohol and repeat.
• Let it air dry for a day.
• Re-assemble and hope for the best.