How old is the unit? It's recommended that fluid be changed every 5 years, keep the jack shafts clean, and if jacks are left extended for long periods that the shafts be cleaned/lubricated with silicone. A bit of debris under a seal can allow air in and leak down, so run it a few cycles and see if the fluid turns pink/foamy, which indicates the air. If it is in fact leaking internally, replace the jack.
David & Danna
2020 Magnitude BH35