Lionel Culvert Unloader 345 (6-12983) Issue

I recently acquired a Lionel Culvert Unloader 345, the more modern 6-12983 version. The issue I have is that the motor assembly that rides on the beam does not sit square on the beam which causes it to slip and either stall on the beam or not deliver the culverts correctly.  I did not see any way to tighten things up to have it sit square.  I was able to work around the issue by adding a 50 gram counterweight to the hang off the end of motor that and seems to have balanced it out. It seems to run ok with this but does anyone have a better fix for this?

thanks,

Kevin