Hitachi EX60URG not spinning

HI Everyone, Can anyone help me with my Hitachi. My ex60urg would not spin so I pulled the swing drive unit out had it rebuilt & reinstalled. it worked great for three days then it stopped spinning. We took it out & sent it back to the rebuilder he said it was good but we may have had dirt on the line when put back in. So we reinstalled the unit , still not spinning. All fluid & filter were replaced. Any ideas? Michael