grease the mast channels
they might be dry

dont use too much just get a thin layer on 1 side of each channel that the carriage rollers go in, the rollers will transfer the grease to the other side of the channel
too much grease can stall the rollers and cause damage to them and the mast channels

also make sure the side thrust rollers arent loose or broken and may be jamming up the works (again in the carriage)
theyre held in by 2 bolts each and they have grease fittings too

look for anything binding the free lift cylinder

in the bottom of the the piston rod itself there is the valve that limits the flow of fluid that can escape if the line loses pressure (burst)
maybe that has an issue

good luck