PA1 immediately dropping call

Hi, I have two SNOM PA1 devices, pn 00002226. I can call both devices, both pick up, but one of them immediately hangs up.

I am testing by using pjsip (pjsua) directly from my computer to the device. They are both set to defaults, with the exception of setting "SIP: Network identity (port)" to 5060. On the device that immediately hangs up, if I set "Require PRACK:" to Off, it will drop the call in 5 seconds instead of right after it picks up. 

The devices are running different firmware versions. The one that works is running snomPA1-SIP 8.4.23 62404 and the one that hangs up is running snomPA1-SIP 8.7.3.19. Firmware won't update, or I would have tried what I think is the latest (8.7.5.75). I followed the manual instructions and tried several iterations of links (all which will download when I test them in the browser). I also tried updating to something on or before 8.7.5.44, which also did not work. 

Is there some setting that I am missing?

Attached are the logs for the sessions:
working call session.txt 

broken call section.txt

We actually resell these on our store, but I couldn't find anyone that has a business/partner contact. 

Thank you!