Sounds like you may be having a couple of issues.
First thing to check, with the box blade on the ground, fully extend and retract the cylinder several times.
Then set the adjustment how you would normally have it.
Mark the ram with tape or a felt pen.
Disconnect the hoses at the quick couplers.
Raise the box high enough so that all of the implement weight is held by the 3pt hitch.
Wait 15 minutes and see if the top link extends.
If it extends more than 1/8" in that 15 minutes, you need new seals for the cylinder. 1/4" per hour is what I consider acceptable with the first 15 minutes allowing for a little more for compressing in the hoses. (expanding the hose)
If it does not move excessively, then reconnect the hoses and do the same test and check those results. There is a good chance that your valve leaks some internally, this is very common.
Not sure about your other problem with the loader.:ashamed:
Please let us know your results.
