I have a gammill on a 12 foot table. In that last 6 inches of travel at the far side of the pantograph the power cord and the coiled cord for the speed regulator will make contact with the table frame. Make sure these are not tangled or catching which would feel like pulling.
You should also make sure the pantograph stylus is not bumping against the take up roller in that area. It would be helpful to have a friend move the machine back and forth though the trouble spot while you look all around for anything touching where it shouldn't
Don't overlook the channel lock magnets when you do this.