Yes, I do have issues with the AirPod Pros at times but it’s only with one person, and everyone I FaceTime (obviously) has an iPhone. So therefore I narrowed it down to the noise cancellation being the issue. I read, after posting this, another comment about the case being too tight around the edges of the phone. Well, Low and behold, as soon as he took his case off and went back to watching TikTok‘s while FaceTiming me, I could hear him clearer than ever before. You see; anytime audio is being omitted from the speakers while they are talking, the mic cancels all noise, and you can’t hear them. But, this only happens when there is a certain amount of blockage (like a case, or standing the phone up right on a surface that covers the speakers and mic) and makes it impossible to decipher even one word out of a sentence.
in short: try taking off the other persons case, and have them hold their phone normally (not in their lap surrounded by blankets, or stood up on a table) and see if you still have the issue. For us, it was the case causing the mic to trigger ambient noise cancellation.