Hello, I'm experiencing this issue with my Pixel XL (first generation). Currently operating Android 9:

Security patch level: October 5, 2018

Baseband version: 8996-130181-1806061856

Kernel version 3.18.1-g2513d25 #1 Wed Aug 15 21:24:02 UTC 2018

Build Number: PPR2.181005.003

I've gone through the "Reset Wi-Fi, mobile & Bluetooth" option at least three times. Once without doing anything additional; once followed by a power off and power on; once after clearing/stopping all running applications and then followed by a restart.

I've been experiencing issues with MMS (primarily group chats) with only named contacts in the last several weeks, moreso in the last four days. Today, MMS is totally nonfunctional. I'm using the native "Messages" application within the phone.