[StuBeeDoo]

I've got a DS 3503 controller that seems to be "acting weird".  I bought it a couple of years ago.  I'm not good explaining, so please bear with me.

Two completely different cars keep randomly stopping while I'm using the DS controller.  If I swap to my spare SCX Pro-branded Parma controller the cars immediately run perfectly.   This only seems to be happening with the two cars, at the moment.  I have other cars with the same motors which seem to be running fine with the DS controller. 

Both controllers are 45ohm ones.  One car has a PSR 16k FF-050 motor, the other has an RX-42.  The PSU is a 12v one. .......And the first thing I did was clean the wiper contacts with proprietary contact cleaner, which made no difference.
However..........  If I swap to my SCX 14v PSU, the two cars will run loads of laps perfectly with the DS controller.

Do I assume that the DS controller is slowly dying?

Thanks in advance,
Stuart.