I have three Pixel 6a phones, all purchased within 60 days of each other and all following the same recommended install process.
One of the phones refuses to make or accept calls when on a WiFi network. With one exception, the phone settings are as identical as I can make them. The phones run SIMS from the same carrier. The one exception - the phone which will not make/receive WiFi calls has the GrapheneOS Sandboxed Google Play apps running for the primary user account. The other two phones do not.
I have updated, rebooted, reviewed and matched all network settings, etc. The troublesome phone will often (but not 100%) successfully initiate a call after a reboot, but it won't do so again an hour later. It won't receive calls at all when on WiFi. All calls go straight to VM.
Any guidance, ideas and suggestions on how to debug, diagnose or eliminate this problem are appreciated.