Are there companies that can check to see if DVR's are Faulty?

I have Sagem DVR / freeview box and after 18 months the hard drive seems to me to be sticking / faulty. It records fine and then on playback it hits a problem and then stops and goes back to live TV. I am finding it difficult to find anyone who can carry out a report in order to present to the retailer showing it is not fit for purpose after such a short period of time (hard drives should not fail after 18 months) Can any one suggest anything? Many thanks

Greg
June 2009