Just saw your video- looks like your hoist cyl is air bound. This could explain the extreme lowering speed as well. When the forks are fully lowered the hyd tank should be full- can you physically see the oil in the tank? If so- is it foamy looking? If it's foamy- it's either the packing on the hoist cyl s*cking air while lowering (not probable but possible) or there's an issue with your hyd pump on the suction side- either a bad connection in the hosing or the pump itself is bad- check the tank & post your findings