Hello,
As for why it would not pass WAN traffic I would have to test and see if I can duplicate, I have a few Decos here. I do know that sometimes they like to have a manual DNS entry of 192.168.225.1 but generally that doesn’t effect the data traffic.
Here is an explanation on the 192.0.0.x address: Why Does My Device Receive a 192.0.0.x , 192.168.225.x, 10.172.72.x , or Other Private IPv4 Address?
T-Mobile thing.
Try setting the InvisaGig to 5G NSA, SA disabled under the Connection configuration and see if it happens any more. This does disable the use of SA bands, and may be more desirable to have SA, but it does also eliminate the 192.0.0.x interface the modem can create when on SA mode.
T-Mobile is rolling out new changes to the way they handle static IPs and I’m starting to think SA use as well. Many people are reporting odd connection issues on multiple modems on Tmobile, but not a ton of people.