It sounds like you may have one of the trucks binding or not turning far enough. I would turn the engine upside down and appling enough pressure to equal the appox. weight of the engine turn each truck back and forth to see if it does bind and has full range of movement. Being it continues to run I don't think you have a contact or electrical problem.
I have to admit when I saw the title all I could think of was Yoga or Hare Krishna :-)
But I think Mike's probably correct. Two other things to check: (1) make sure the wheelsets are in gauge (you could get binding like this if one wheelset is a little wide) and check the track gauge. For both all you need is an NMRA gauge, a good investment.
I also agree with what Mike has already stated. Do test the range of movement on the trucks, because it could be as simple as a pickup wire from the one side not long enough to make a good swing for that truck.
Also check that the worm and top gear are meshing properly. I don't have a SD60 but on all the Atlas locos that I have if you look at the truck from the bottom the slot for the gears goes to the right hand side.