@Simmonz Can be worth playing around a bit with APN settings for MMS. I needed two separate APNs for Internet and MMS. I was able to use a tethering APN for my Internet and the nornal one fot MMS. Some seem to need this, others have found the opposite, that it only works with combined Internet and MMS on oneAPN setting.
I still lose about 1 in 10 of incoming MMS messages, but at least I get a notification.
If you're able to test VoLTE, I'd be very interested. I believe it should have a VoLTE icon in your indicator bar at top when connected on a call if it's working properly. Insights on call quality, and whether SMS works normally with VoLTE enabled also welcome.
Too bad about reception. Not sure why it would be worse with same device on UT vs Volla OS.
Thanks for the info!