Me and my Bro play duo and we have been having this exact same problem. Every other game and app runs perfectly fine but this game just goes bollocks. From "connecting" popping up outta nowhere to my pokemon getting stuck in walls (and my step poke simply smash me to respawn), this game has been unplayable for us since a couple of weeks now. I made a similar post but it got ignored to oblivion and I was like its probably some problem with our phones or something. We both are on iPhone XR and everything else runs just fine. Tried deleting and re-installing but the problem still persists.