i've had some experience with these push-pull attachments
in most cases where the sissor assy is being damaged it is usually due to the operator ramming into loads or trying to push loads. I did alot of work for Hunt-Wesson when they were in my area and almost always it was due to the operators having to pack the product into a boxcar by pushing it into place. They had to pack the product in very close quarters and it always didnt fit exactly so they would try and force it into place. This would put undue stress on the extend/retract arm and would almost always bend or break something in that mechanism.

Also there are some adjustments and pressure settings that need to be checked to make sure the unit is not operating overpressure. Check the rod adjustment on the extend/retract cylinder and also make sure the forks do not have any "curls" on the end of the forks from impacts, these can cause the loads not to slide properly and can cause the load to hang up.
the leaking is due to the cold environment shrinking the seals in the cylinder heads. You should contact cascade and see if they offer any type of special seal kits for freezer applications. I dont think they do though, you may have to find a "seal making" vendor that can make seals and have some custom seals made specifically for cold environments.

Changing the oil in the lift to a freezer type oil might help somewhat but i dont think it will totally. Chances are the lift already has freezer oil in it, this should have been factored into the options when the lifts were purchased.