My girlfriend's Fairphone 3+ got wet in rain-drenched clothes. She then tried to make some calls, but first couldn't hear the other person, and later people also couldn't hear her. Then, the phone died.
We then disassembled the phone completely and laid the parts out to dry for a day.
I noticed some white corrosion on the connector for the top module, and after cleaning it with alcohol, it's visible that one of the pins is darkened.
Take your working phone. Swap in one component from the broken phone, test if it works. Remove the part from the broken phone and put back the known good part from your phone. Repeat for all components from the broken phone until you have found all the broken parts.
That way you can test each component in isolation.
Annoyingly, I can't fully take the phone apart with the supplied screwdriver, so I can't check all the components and connections...
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