the mast is 4meters and it would hang up at around 2meters.
*without load, it has no problems.

my observations/guesses are:
-control valves should be working fine, because without load the mast goes up and down with no problems.
-hydrualic oil if full, no leaks.
-loaded, mast can go up and down around the 1meter height, but higher, around 2meters it would get stuck (or it will slowly shake going down as if it is misaligned). i havent tried it loaded going up and down from the peak.
*would the mast bearings have anything to do with the problem? or is there another cause you can think of?

thanks!