3 year old Spectrum EZtrack Christmas trolley auto reversing worked fine first 2 years, then this year worked fine for about 1 week, then started running extremely slow for a week, but always reversed at both ends.  Then for the last week it would travel to the bumper end and stop, and now it will not travel at all.   I have cleaned the track rails, and cleaned the wheels on the trolley.  There is voltage to the rails....Any suggestions?