I'm not saying this is going to solve your issue, but have you asked to exchange your modem for the newest XB8? Just throwing it out there in case it's something weird with your modem. I had a similar issue a bunch of years ago with a Rogers Gateway...
Which part of Stittsville are you in? I switched over to Rogers 1.5Gb service a month ago now, and have ZERO down time. I am also in Stittsville. I use a UDM-SE which monitors connection, so I can see if I am down for even a minute. And since I ha...