I purchased a E-Z Digital Command Control System (BAC44902) this year in May.

I have two Bachmann DCC locomotives that I use.  Since I purchased this, occasionally when the speed control was turned all the way off, the locomotives would continue to move at a slow speed.  Now this is happening almost all the time.  This happens with both locomotives, so I don't think it's the engines.  I feel it must be something in the controller. 

Has anyone experienced this problem?  Is there something I am doing wrong or is this a defect?