I have recently developed issues with my modem. I have an Arris SBG7580-AC which I own. Comcast "updated" the modem from their end and it worked for about 10 minutes before going down again. Unplugging and plugging the modem back in does not restore service, but restarting the modem from the modem's local webpage does, at least temporarilly. The modem is a combination modem/router, and the entire unit has also spontaneously restarted several times. The issue has been going on for >24 hours.
Comcast has scheduled a technician to come tomorrow. In the meanwhile, I have called Arris, who has said that the issue is because my upstream power is slightly out-of-spec. From a brief Google search, that does not appear to be the case, but I was hoping anyone with some knowledge about this could comment on whether or not there are any abnormalities on my modem's Parameters or Event log.