I have a 136 RX-1 and haven't had this problem at all.
I'd probably pull the skid out and give it a good look over, make sure nothings too bent out of shape that would make the track run funny.
Also make sure that he has the correct spacers and washers in the rear axle, if something is missing he could be putting side pressure on the wheels from the nubs in the track.
Obviously make sure the track tension and alignment are good when everything goes back together.
I assume if this is a 136 RX-1 that he's running rail extensions? Is he using extensions that extend the slides or just the ones that move the axle back?