Delayed text messages

I've been on US Mobile (Dark Star) for the past 6 weeks or so, and I'm being told that many text messages sent by people using T-Mobile can't be sent on their side. It shows as not delivered from their side. The texts eventually come through anywhere from 1-10minites later. I'm using a Pixel 8 Pro while other folks vary from iOS and Android.

Phone calls work fine and come through immediately so I don't believe it's a signal strength issue. Interestingly, I've noticed this happens mostly when I'm connected with 5G (not 5G+) and in one specific place (my office) which is problematic.

I never had this issue with T-Mobile before.

I tried disabling Android's Adaptive Battery feature and that doesn't really seem to make any difference. Having the phone unlocked and the text message app open seems to sometimes speed it up, but not always.

I can't switch to a different network as I'm on the Dark Star BOGO plan (Unlimited Starter).

I'm at a loss for what to do.