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DSC is the traction control system on the car.
if the light is flashing and power is being lost, this means that DSC is sensing that the car is losing traction and cutting in to correct for it.
if the car is in fact not losing traction, then this means that there is a fault in the DSC system which is causing it either to erroneously detect slip when there is none, or cut in randomly.
there are many sensors which inform DSC and a control computer, so any of these items could be the cause. You will need to have the fault logs read from the vehicle and possibly the DSC systems monitored live with a BMW diagnostic tool to verify where the issue is arising. Most likely it would be a faulty wheel speed sensor or faulty control computer that would cause this.
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