I am not familiar with the mechanics of the machine, but a good place to start would be to jack that wheel up and see if you can get movement by pushing on the top of the wheel towards the axle tube. If so that would indicate loose bearings, or perhaps badly worn bearings.
If you can't move it, try with two people, or put a lever such as a shovel under the wheel and try to lift the outer edge of the tyre.
Next, try to do the same thing with someone else applying the foot-brake. If the movement goes it may the bearings; if it stays, it might be worn or loose swivel-pin bearings. I can't remember what type of swivels the International use, so I may be wrong here.
If there is nothing obviously wrong after doing the above checks, it might be whatever type of joint is used to allow the axle shaft to bend, when the steering is used,
Cheers Charlie