It does sound like a door check problem and would be expected at this age. Typically, the check wears and allows some of the "BB" sized bearing to work loose. There is also one large spring loaded metal bearing that is used to engage the different door position "stops" that might be stuck. It takes about a half to an hour to unfasten the door panel, undo the hinge pin on the chassis, unbolt the check and lift it from the door. Replacing goes much faster. I've noticed that the new door checks come with a plastic sleeve that keeps the check dry and the lube in place.