SKY Digibox does not seem to hold signal for more than 30 seconds??

We have an old skydigibox, a Pace DV3 about 7 yrs old that we use with a sky freesat card, they issued a new one to us just before xmas. Last autumn for a few weeks we were getting a problem that in the evenings the signal would vanish then all of a sudden it was OK. Now we are having problems again ... every channel says " no satellite signal" but if you go through the sky info and re-set you get it all come on for between 30 secs and 2 mins max. Obviously there are no problems with the dish or nothing would come on so is it feasible the box is knackered?

Dont want to go and buy a new box and find still a problem? Any ideas would be appreciated as Im disabled and TV is my only entertainment as Im on my own?

Thank you.