You have an unusually difficult problem, and until you can pinpoint the cause (e.g. by using an oscilloscope), only guesswork can be offered.
Even the "slight pulse" you mention (using the other motor) is cause for concern.
You have an unusually difficult problem, and until you can pinpoint the cause (e.g. by using an oscilloscope), only guesswork can be offered.
Even the "slight pulse" you mention (using the other motor) is cause for concern.