Upload speeds capped at 5mbs.

I'm on the "superfast" plan and should be getting 800 down / 20 up, a few days ago however I noticed my upstream was being capped at 5mbs (and download at 700mb). I ran through all the usual troubleshooting steps, and none of them seemed to help. Doing some searching around this problem is common when your modem receives a default "bootfile", this seems to happen when your modem doesn't support the speed plan you're on. I own an Arris surfboard sb6190 and it's been working just fine for years, according to xinity's own compatibility list it should have no problem with 800 down and 20 up. However, seemingly out of the blue I'm now being capped far below what I should be receiving. I've already contacted customer support over the phone, I asked them to reprovision the modem on my account hoping that it might've just been some mix up on the back end. They tried to reprovision it, but honestly I'm not sure they were just sending reset signals to the modem or even understood the problem.

I'm a bit at my wits end here, the modem was working without issue 5 days ago. The connection is stable so I don't think its an issue with wiring or anything like that. Any help or suggestions would be greatly appreciated.