mike, read the replacement bulletin again. if both ends creeps out, it is the extend solenoid. not the retract solenoid. that thinking is exactly the reason hwh recommends replacing both solenoids. you cant miss.
i dont mean to be critical, but its a costly mistake to replace the wrong one. for a test of this theory, just open the extend solenoid when the slide is retracted. it will move out 3 to 4 inches. if instead, you open the retract solenoid, with the slide closed, it wont move.
if both ends of the slide only moves out 1 to 2 inches, it will likely be the check valve.
thats why proper diagnosis is so important.
if only one end moves, the room cylinder or the sync cylinder is suspect. if there is no external leak, you will need a couple of pressure gauges,and a shutoff valve to diagnose this problem.
low fluid will not affect creeping. if the slide moves all the way out, and all the way in, the fluid level is not part of the problem.