Hi and welcome to Digi Forums.
We do have other customers using our devices with Palo Altos successfully. (most of the time we are actually the initiator rather than the responder but that should not have any impact)
There are several things that can affect a tunnel behavior as well as several configuration options that could help to rebuild it, for example:
eroute n autosa 0
eroute n nosa drop
ike 0 delmode 3
If you are already in contact with our Support Team, I would suggest to continue working with them via our case/mail system as this is the right place for such troubleshooting.
If you did not reach out to the Support yet, please send a mail with all details at firstname.lastname@example.org
You can view all details about our support and support policies here: https://www.digi.com/support
Digi Technical Support