well, you found the solution before I saw your thread, glad you figured it out..
the friction of the packing and seals in an old hoist that hasn't moved in years is going to be tight..
pressurizing it with air instead of hydraulic fluid furthers the friction without the lubrication of the oil surrounding the packing..
I was looking for some references to post to help you and found this;
https://www.garagejournal.com/forum/...ad.php?t=45725
PLEASE READ POST #16 before you do anymore experimenting.. and take note of his job title and company..
https://standardus.com/contact_us.html looks to be only a couple of hours from you
my advice would be to locate as much information about the hoist system and call a lift company for assistance..
good luck!