Replacement earpiece didn't fix problem!

The earpiece on my iPhone 6s Plus stopped working several weeks ago when my mom spilled half & half on my phone. I ordered the replacement piece and installed it- which worked fine for about half a day, then it cut to 50% volume even with the control maxed. I re-opened the phone to make sure the earpiece was seated correctly and it was. I see no signs of water or liquid damage around the earpiece, and the Facetime camera and light sensor work properly.

I just installed a second replacement earpiece, and it seems nothing has changed (still at 50% volume).. And yes, I cleaned the mesh!

Any tips on where to go from here would be greatly appreciated.