I only post recommendations that people try chan_sip when people post a comment stating that they’re having trouble with pjsip. Using chan_sip when you have trouble with pjsip is always a good trouble-shooting step.
There’s a post on the forums right now about a pjsip bug relating to NAT. And it is a bug that I’ve seen myself. Here’s one:
Thanks for giving me this chance to convert you. I assume that you’re in my camp now that I’ve given you precisely what you asked for!