iPhone 6s Low Earpiece volume after replacement

My wife's iPhone 6s recently started to sound very quite when she was talking with people. She thought it was just her, but I verified the low earpiece volume. Proximity sensor, front facing camera both work properly.

I have tried multiple fixes. Changing language setting (En to UK and back). Replacing the earpiece, and cleaning the screen. It also has the most up to date iOS.

Also, I have done the voice memo test to see if it works better, but unfortunately it is still the same low volume.

The only thing that I know of and have not tried, is poking a small hole in the left portion of the screen. I see this as a last ditch effort, and prefer to leave the mesh intact.

Any other options that may work for me? Thanks in advance.