Why do I get a black screen when I call someone?

I have a first gen Moto X XT1060. I recently did a number on it (Water Damage) and had to replace the board, battery, nfc coil, volume/power flex, and some screws. The proximity sensor does not work anymore, meaning if i call someone or if someone calls me and i answer, i get a black screen with us talking. Either they have to hang up or i have to restart my phone. It gets annoying and i would like to fix it. If anything, I may need a new gasket for the sensor. If I do, could someone direct me to a page where i can by one?