Dell 924 AIO Printer

Recently my 924 Printer has developed the habit of failing to feed paper reliably i.e. 1 in 3 attempts to print fail because the paper is not fed into the mechanism. I have taken the printer to bits far enough to see the rollers which are used to grab the paper and feed it down to the print mechanism and watch the rubber rollers revolving but all to often the paper does not move. I have tried paper from different manufacturers but the problem remains. If I manually force the paper down it usually works ok. The printer is 2/3 years old but does not have a hard life as I do not print very often.

Any ideas would be appreciated otherwise it will go to the tip and I will never buy a Dell printer again