A bit of a stretch, but since you are getting the WAN disconnects, have you tried a different modem (or equivalent)? If it's ISP owned, you could ask for a replacement that it's ideally from a different brand and or model.
As far as I know, still supported. But it has reached the stage where the cadence for updates is slower (like most routers out there). Mine has been rock solid for the last year. If I was to buy a new one, I'd go with the RT-AX86U Pro or GT-AX6000.
Like Igs said, most likely, nothing. That log item is fairly common. I think you get that if you disable auto-update or the update server is down/unreachable.