Thanks for the replies everyone. I submitted another online order and it registered without a fuss. In fact, I think they processed my original order despite saying it wasn't supported because I received two order #s and had to call in to cancel one of them.
I would very much like to hear Teksavvy's official stance on this. They sold SB6121 modems to customers with firmware less than 18.104.22.168, are they fully supported? If not, will Teksavvy do the trade up program?
TSI Marc or Martin, it would be very much appreciated.
Reps are telling me to pay another $99 to buy a new modem from them, since neither I nor they can do anything about this firmware garbage. It's been a good run, but I am not paying another $100 for the same modem with a new number on it. I cancelled, now I have to hunt for another provider.