Rear Window Gear Problem

[pbgsho]

After rebuilding both of my front window motors and installing them I now am now able to operate them with no problem. I then tackled the passenger side rear window and rebuilt it with new window regulator gear plugs. Motor runs fine in both directions. After installing it on the three threaded studs, the gear on the motor does not mesh with the window regulator gear, hence no window movement. The gear teeth on the regulator appear to be fine with no apparent wear.
I debated drilling out the regulator rivets so I could move it and attempt to mesh the gears but this might result in bigger problems. Has anyone encountered this problem before and if so what was the solution?
TIA,

pbgsho