Been there done that! When I did the hydro assist mod for my first box I must have been sleeping , couse I put the piston in 180* out then whn I reinstalled the sector shaft the gear came in contact with the tube the balls go through. Needless to say there was some damage and the balls bound up and spit out into the housing. So I was back to square one and I had to start over again with a new box.
My box did exactly the same, hanging one direction then the other, for a secon I thought all was good. Just as I got in a tight section trying to make a turn around a tree, there was no more steering. I could spin the wheel all day long in either direction. After diassembeling the box The carnage was unbeliveable. Some of the balls were imbedded into the piston and the o ring and nylon seal serfaces were trashed, along with some of the balls getting smashed to bits.
Time to source a new box!