Before deciding that your motor's at fault, turn everything off and let it sit for a while (to discharge the capacitors), then switch the leads from the X axis motor with another motor that's working okay. Then see if the fault follows along, in which case it's likely a problem with the drive, or if the same motor still doesn't work, confirming your first theory. If it's the drive, Gecko might fix it for you for free. They'll also be happy to recommend a motor suited to the G540 - probably because so many people ask this question, they've started carrying them themselves.
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