spool and sleeve might be binding, similar effect (spool binding) if that center pulley screw is set too tightly in the older assembly SA describes. Also possible the spring isn't loaded properly (as a result, spool doesn't rewind tightly enough). Believe the basic procedure for changing rope calls for turning the center screw or bolt (spring retainer) 20 turns or so counter clockwise, temporarily locking the spool in place, installing the new rope, then letting the spool slowly rewind clockwise wrapping the rope. Spring should have the right tension at that point. Assuming nothing else is binding, it should work fine.
Recommend finding the instructions, and having then handy when doing this. Spring assemblies are dangerous.