I have a solution to this issue
Today my tail lift unit failed for both open and close
I removed the drive unit and dissasembeled the denso 12v dc motor from the gearbox to find the motor caked in burnt grease that had drippped into the motor case from the open gearbox
The brushes and contacts on the armeture were gummed into oblivion
Cleaned it all out very carefully and now it runs quiet and like new
My suspicions arose because it sounded like to motor was always working too hard for what it was doing.
If your tail lift partially goes up or down then returns this is likely the overall cause of the issue.
You have to remove the panels from the door scuff,tray and side pocket to get into it as its all installed in steps also the cup holder has a screw at the front to get before you can romode the lower wall panel to take off the upper wall panel.
Much easier to put back together.
