Hi, I also have an MG series.
If it's like mine, you have a rack and pinion drive on the x-axis. To check for binding you can disconnect the electrical on both motors, then unbolt and remove them. the motor is mounted on a plate held in place by 4 screws.
With the motors off, you can then move the gantry by hand to check for binding.
Unfortunately, they didn't spring load the pinions, and the profile guide rails are mounted directly to the rack, so as the wear on the rails progresses, you get to a point where when you tighten the pinion enough to take the backlash out in the "heavy traffic" area, it then binds when the gantry goes to a place with hardly any wear.
My machine spent most of it's previous life running about 5 kinds of speaker cabinets, and it's looking like I might have to put some fresh rails and trucks on.
Good luck, and keep us posted!