Nexus 6P proximity sensor not working after changing LCD block

Due to water damage I had to replace my LCD block, since then everything works fine but the proximity sensor.

As a result, my screen turns black as soon as I make a phone call and I have no way to terminate the call (I now have enable the `use power button to end call` under the accessibility settings).

With the AndroSensor app, I can see that the proximity sensor reports `0 cm` all the time.

I suppose the issue comes from the repair I made, but I need directions on where exactly to look at inside the phone to diagnose/repair this.