See that orange thing? That roller is most likely the culprit.The first step I would make is to make sure that he is transformed properly and none of his treads are dragging on the ground. Also make sure to transform his groin plate because that can get in the way also.
If that does not help, try to spin/flick the roller it with your thumb. If it barely moves then it most likely has burrs. Very carefully pry it out by using your fingernail to spread the prongs gently. You only need about a millimeter of give and you can pop it out with your fingers.
Got that sucker out? Good.Now all you need to do is feel for burrs because it is hard to see them with translucent plastic. Do be mindful of the peg in the center. DO NOT sand that off or you will break your Hardhead.
Get yourself some fine sandpaper and sand them burrs!Be VERY CAREFUL not to sand the peg because then the roller cannot be placed back into the prongs. The peg is more of a tiny little bump so you must be extremely careful! I used some super fine sanding paper that was in my toolbox. It reads "TUFBAK DURITE T446 600-A" I am not sure what grit that is but it worked like a charm!
Now just pop the roller back into the prongs and you are good!
As Emgo would say it rolls like rolling things should.