It was a bug with the B6 and T1 where if there's no command base present, the tender light would flash indicating that it wasn't getting a TMCC signal. I tested Bluetooth a lot in these, but never thought to unplug my command base!
We have code for the B6 and T1 available to customer service, so if you send the engine in, we can reflash it and it'll be fixed. We found the issue before the GS was made, so that and all other steam engines will not have the issue.