The 286 is a good medium-duty rotary, well made and strong. But rotary cutters can sometimes have a hard life.
A quick check you can do without it running is to rotate one of the blades to where you can mark or measure the height of its cutting edge - then rotate the other blade around to the same position and see if the blades are at the same height. If they are vertically off more than about 1/4" then something is bent and needs straightening to get a good cut. With a bent stump jumper the blades can be off 1" or more. While you are under there check all around the spindle for any evidence of oil leaking out of the gearbox. If it's dry, take out the fill plug and check to make sure there's oil in it. If it all checks out, buy it. A comparable new one is $2k or more.