I had same sort of problem in Sept to mid Oct, ISP sent me a Router for Testing purposes and they changed my profile it has been stable since then. For me it looks like either my Voyager 2110 might be worn out or line has got noisy.
Despite being on 12dB profile I gained half a meg in connection speed (was on 6dB connection, then wouldn't hold on 9dB but does on 12dB)
Try changing microfilter and also plug into Test Socket on Master Socket.
Have you looked at router home page to see what profile you are on and your SNR margin?
Have you got another router you can try?