I have been having the same issue. AirPods Pro 2, iPhone Xs. I went to the local Apple Store. They ran diagnostics on the AirPods Pro 2, but all the tests passed. I did find something that may solve the problem. I turned off "announce calls" (Settings -> Siri & Search -> Announce Calls) (set to "never"). Using my home phone, I called my iPhone, while listening to music through the AirPods Pro 2. I clicked the right stem (as I did before), and this time, the call connected the way it should, and I did not experience any issues. I kept the call going for a minute, and made sure I could hear myself on the home phone. I then double-clicked the right stem, and the call ended, as it should.
I think what was happening is that sometimes Siri would announce the call, and sometimes it would not. I'm not sure, but it seems like the "announce calls" expects you to ONLY answer by responding "yes", and if you click the stem instead, the iPhone/AirPods Pro 2 gets confused and results in audio issues as many here have described. This should not be the case, and I consider this a bug, but I will try this and see how it works.
I'm disappointed that the person at the Apple Store did not ask about these settings, or how I was answering calls. Especially after I showed a list of issues I was having.
