I have had this problem ever since switching to bluecurve a year and a half ago. It clears up for a while and then it starts up again. I too have spent time on the phone with their phone techs, I have rebooted the tv boxes, moved the modem to different locations in the room and nothing works. Obviously Shaw does not seem to make resolving this issue a priority and when my two year obligation is up I will explore other options.
I just got the blue curve box about two weeks ago, was fine for the first week but now I am having the same problems, it’s an irritating and if they don’t fix I will be switching systems for sure