Loose coax makes a specific channel lose picture quality?

I work tech support for a company I won't name, and I got a call regarding an odd issue in which a specific channel started degrading picture (and eventually sound) quality during a specific time of day like clockwork for all set-top boxes. I had the customer tighten the coax cable, and when I called back during the time period in question, the issue stopped occurring.

So it seems to me that the loose coax cable was somehow responsible for causing one specific channel, no others, to lose quality during a specific time of day??

How does that even work? I have to call them back on Sunday to check whether it's still working, and if it is, I'd like to have some kind of explanation for this. Does anyone have an idea why that happened?