Digital TV reception is a nightmare !
A lot depends on the make of receiver and the chip installed. Some chips get their knickers in a twist for the slightest reason, others are very tolerant of errors. I live in a poor reception area and have tried quite a few receivers, some good some bad, cost doesn't seem to be a factor. In your case I would be inclined to check out any electrical apparatus in the house. Usually things like central heating system thermostats can cause havoc when they "arc" switching on and off. Same applies to fridges and freezers. Try switching things off for an hour to see if it makes any difference. Good luck.