Probably not. Why don't you try unplugging the sky box for a bit, either from the phone line, from the mains, or both, to see if it makes a difference to your SNR margin. Note you won't need to resync to see if it makes an immediate difference. If so, then take some steps to sort it out, if necessary shove a filter on the phone cable going to the sky box to see if double filtering makes a difference.
So yeah, it might be the cause of the problem, but then again it might not. Like I said in your other thread, we don't know for sure because we don't have the advantage of physically being there!
And like I said in your other thread too - SNR generally will decrease in the evenings, and there is very little, if anything, that you can do about it