The recoil starts moving as soon as you connect the battery.... even with the power switch off? if so then yes you have fried the DMD/MF if not you may want to try another recoil unit just to confirm its the DMD/MF.
For testing purposes you can plug any tamiya recoil unit in.

If you still have the receipt call tamiya customer service tell them the symtoms they may send you replacements. Electronics especially expensive electronics are supposed to protect themselves from overvoltage.... If you don't have the reciept still call them I had missing parts for a T1 I received for christmas and they let me fax the cover of my manual as a receipt.