Homebrew,
You never did tell me if the QA cyl went into relief, and therefore was exerting the full force on the cyl rod.
The reason I ask is that if your cyl is a 1 in cyl, and 1/2 in rod, at 3000 psi, that cyl should exert a pressure of 2300 lbs in the extend mode, and 1700 lbs in the retract mode.
Does your three spool valve work well in other functions?
It puzzles me that the cyl could not pull or push past the lugs.
The only way I can see that the hyd would not work is that if the mechanical force, as in a bent plate might put enough force of steel on steel to overcome the pull or push of the cyl.