Clock will run down to 1 second of the minute and...

Question

Our Dacor PCOR30 over stove microwave stops when there is 1 second left to go on a minute. Set at 3 minutes it runs to 2 minutes, 1 second and stops, push start again and it runs to 1 minute 2 seconds and stops. We recently had a construction company cut the power line to our home. Could this have caused a spike to create this problem. Have been told we need a new expensive timer.