Have you checked your fluid level? Have you checked the supply line to the pump. Is your FNR lever ok? There are usually ball switches attached to the FNR , as it wears the switches no longer close contact like they should. Being a DD12 you should just have a cable from your FNR lever down to the pump controller. That pretty much eliminates any and all electrical except the brake which you eliminated.
Does this "stop" happen in turns, straight line travel, throttle up, vibes on/off. What condition contributes to the problem you're having? When it happens, is the lever still in position of travel or has it migrated towards neutral. If the FNR is still in position has the pump lever come off of stroked position.
Just some stuff to look at. Good luck, let us Know what you find.
Now, I just remembered a job we had, a DD12 it needed a motor, shaft broke .Shaft was integral to motor. Travel is in parallel from pump to one drum or the other and back to pump. If one motor free spins , you loose your tractive effort. IIRC... It all came back to the driver binding the machine down to the point that the frame was almost on the drums when he tied it down.