SB8200 Failed FW update Xfinity

Hi, I recently bought a second hand SB8200 and went to the events log at the web interface and noticed there's a constant 'FW update initiated' followed by a 'FW update failed due to incompatibility' every time I either reset the modem or every few hours or so. I'm aware I'm way behind in FW updates and that my ISP is supposed to update it, but for some reason it can't or it won't take it. I've talked with Xfinity agent through both their app and Reddit, the first telling me that they couldn't see the modem as online and the latter saying that the update Arris provided to them is not good and that this modem has a lot of problems with many ISPs so they couldn't do anything until Arris fixed it. I'm trying to get it updated cause from time to time I lose internet connection and apparently it's because it's trying to update itself but because it doesn't work, it resets briefly, enough to ruin games or streaming, and sometimes connection slows down permanently, needing a modem reset. I hope you can help me