First thing to do is determine whether it's the tractors remote hydraulic outlet not holding pressure or baler gate cylinders are bypassing.

Next time he starts a bale, disconnect the hoses from the tractor and tie them out of the way, then make the bale. Plug them back up when the bale is made and see what that one looks like.

If it's a good tight bale, the problem is in the tractor. He MAY be able to overcome that by bumping the remote lever to keep pressure on the baler. If the bales is loose, it's a baler problem.

The baler can have cylinders leaking by or the bale density valve (the one with the dial you turn to adjust bale density) can be bad.