Call Quality - Specific Phone

I have ONLY one user telling me that people on the other end of the phone have problems hearing her.

I have replaced her phone and her headset. The problem comes and goes and there doesn’t seem to be a pattern developing.

I’ve barged a call where someone was complaining about the quality and it sounded fine to me (same lan). I have about 20 others using the same system and they never have quality complaints. I’m out of ideas, does anyone have other thoughts?

Thanks in advance!

port failing on switch/router?