Case 1845c bucket tilt cylinder sticking

For the cylinder to retract fast, then slow, then fast again when the other one is working normally would have me looking at the hydraulic hoses going to the cylinder that is acting funny. Something like one of the hoses is getting pinched when the speed slows down. Can't remember exactly how the hoses run on an 1845 as to where they split off to run to each curl cylinder. Hose damage would have to be between the main line tee out to the left curl cylinder and back to the other main line tee.
Another option would be something hit the cylinder and egg shaped the tube and increased friction is causing it to slow down. Either the cylinder wall being bent or a hose being pinched sound like the two most likely causes to me. For the rod being bent causing that, the rod would have to be bent rather far and most likely the end of the cylinder that the rod comes out of would have to move against something to cause the piston to bind up in the cylinder.

How much stroke does it slow down for, like are we talking 3 or 4 inches or a foot or more?

That is a lot for it to be a bent/egg shaped cylinder.
I can see one of the cylinders moving easier than the other if they are both unhooked from the mounting plate.
If you take two hydraulic cylinders and hook up the hydraulic lines, when you put fluid to the cylinders they will not both move the same distance at the same time. You should be able to hold either cylinder from moving by hand as long as the other cylinder has stroke left in the direction it is moving.
But I can not see them putting enough twist on the plate to bend it without something else being wrong.
Any chance the pin that attaches the plate to the boom is seized up on one side or the other?
Just throwing out any possible thoughts as they come to mind.
I saw one once that the stops were welded on incorrectly at the factory. And hitting the stop on one side before the cylinder bottomed out caused the plate to bend, making it very hard to switch attachments. Can not remember what make that machine was.
I am a Cat skid steer guy so I am not exactly on top of how Case has the 1845 set up.
They are all just about the same, line from valve out of machine, up across the boom, tee in line to run to each cylinder. Then line from each cylinder to tee and single line from tee back to valve.
I know a guy that has or had one, if he still has it i may ride by his place to take a look.