Modem Manager won't permit fast.t-mobile.com APN

Greetings,

My phone reverts to fast.t-mobile.com for the APN in Mobile Settings. Which is not an issue, I've had other phones do the same without issue. (US Mobile, using T-Mobile service in USA)

I'm having issues keeping data services working proper, in particular as I travel between cities, or if I power off/on phone.. In order to restore service I need to toggle to a different APN, the back to the fast.-tmobile.com APN. This usually works.

As I attempt various settings to resolve, I notice the APN entry in Modem Manager GUI is incorrect, it puts fast.tmobile.com as APN, missing the dash. I am unable to edit to proper setting, it does not accept the dash.

Now this could be purely cosmetic, I am unsure, could this be a problem?

Photo will be attached.

Thanks!