APN Issues - T-Mobile

I recently purchased an Orbi LTE LBR20 and have been using it with a T-Mobile data only SIM that I obtained directly from the T-Mobile store.  For the first few days it has worked great with the auto configured settings.  About a week into using it, I noticed that the pink light was lit and found that there was no internet.  A little research here and there and I ended up messing with APN settings.  I found that if I change the APN setting to anything (and I mean - ANYTHING (even my name) other than fast.t-mobile.com the Internet connection is restored.  Obviously this isn't a correct setting so I factory reset the device and once again after about a day, I had the same issue - no internet.  I go back into settings and for kicks I change the APN to something other than the fast.t-mobile.com and it starts working again.  The APN field is required and it doesn't let me leave it blank.  Downgrading the modem firmware to A05 and upgrade back to A06 seems to correct the issue for now. 

Firmware is 2.6.4.2 (router)

EG18-NA-PAR01A06M4G