I bought the thicknesser on the offer but have only just started to use it. The first board was fine, but on the second one, the feed rollers seem to have stopped working, as you had. Did you solve the problem or did you return it?
For anybody else that has the same problem, I found a video online of a de Walt planer thicknesser being repaired and it was close enough to show how. I used an SRAM 3/8 single speed chain which is a bit thicker than the original but works OK, so far.