Check fluid level with the cylinder retracted. If fluid is low, pump could run out before cylinder is extended...
From the manual
5.Air in the system will usually cause noisy operation or cylinder will creep down enough to set off alarm.- To purge, extend the levelers in pairs to full extend, (hydraulic lock) for 10 minutes. Bump "all retract" switch then fully retract levelers.
6.Cylinders are self sealing- after the purge above, retract only 1/2 way stop for 5 minutes, fully extend for 5 minutes then fully retract. (Note says to always bump "all Retract" switch first to reverse pump motors before retracting. )
7. Cylinder will not lift coach- Make sure system is plumbed correctly. (left port on motor to top of cylinder)
Check needle valve in pump assembly? or replace cylinder.
(this sounds related to your problem but the manual is sparse on details)