Gnome Calls - Crashes Immediately at Start of Call

I have two devices running Fedora Workstation 36: One is a clean F36 install on a Dell XPS15 5920 (2022) laptop. The other is is a mini-desktop that has gone through a few upgrades since Fedora 34 to get to Fedora 36. So different hardware but same O/S version.

Both devices have other SIP clients installed that work perfectly. e.g. Blink. Using the same SIP account with Gnome Calls, (provided as part of Fedora,) I can get the account to register in Calls so Calls tells me I’m “online”. However, whenever I start any call with Calls on either of the devices, Calls crashes within one second and just disappears off the screen. I couldn’t spot any obvious error log but if anyone would kindly share how to get Calls to log a failure, I’d of course be happy to test and share any log information.

The SIP account details are correct and have carefully been compared to the entries in other SIP clients that are working on the same hardware, with multiple attempts to reinstall and set up over some hours. I’ve also disabled the firewall temporarily in case I need to open additional ports, but that didn’t help. The SIP provider is PhonePower, one I’ve used for over a decade. For example, with port 5060 (not the default port 0 that Calls comes up with) and the UDP protocol.

If anyone has any constructive suggestions I can try on Fedora, I’d be very grateful. Would love to be able to eventually switch to use Calls as it seems nice and simple and easier to use than some other offerings. (The only UI thing missing for me is you can’t set the delay interval between registrations which some SIP providers require, but that is something that probably is better documenting on the Gnome site.)