Service drops out intermittently, but most of the time

For about a month now, most tv channels have been intermittently inaccessible. I get a variety of error messages saying "we're having trouble connecting," or "something went wrong," or something else that suggests there is a problem Xfinity is working on or that it's just a temporary thing. But it's been going on and on and on. The service is at a weekend home, and we've had a service guy come out a few months ago to deal with a similar problem. He said that there was a problem at the pole and that Xfinity would come deal with it the following week. I have no idea if that happened, but I do know that most of the time, I can't watch TV. Sometimes it will be fine, but then go south after half an hour or so. Sometimes some channels work while others don't. Oddly, the DVR seems to be able to record most things, but not all. And here's something key: Sometimes wiggling the connections leading to the cable box seems to cause channels to come back, but then it goes south again. I've tightened every single connection within an inch of its life, and then replaced the splitter and the cables from it, but it hasn't helped. Most annoyingly, I can't seem to find any way to get Xfinity to send somebody out to deal with it. So, here I am posting. Any thoughts?