Is my timer broken?

I have a Hotpoint WT960 washing machine and the cycle times are taking longer than they should - approx 25 minutes. It counts down to approximately 43 mins from 60 and then jumps forward to 55 mins again. It does this a couple of times during the cycle - counting down correctly and then adding 10 mins back on. Could this be a timer problem or what else could it be? Thanks in advance.