99 dodge stratus, rear disc caliper?

if it has anti lock brakes they will do this also,and you do have to remove the cap off the reservoir so the fluid has a place to return to,when i did mine they felt like that until the piston got almost all the way in, then it got real easy to turn in,so you could have a bad caliper causing this too happen also,myself i have never had a problem from the lines as much as from the calipers being stiff on them,that would also explain the excess wear you had on the one side of it,good luck.

To me something is restricting the flow of fluid and I'd be checking for rust in the system such as in the fluid and rusty brake lines or bad flex hoses etc.

Hope that helps and best of luck.By the way from what you say the front brakes need checking asap and that caliper and others could be sticking.

Did you take the cap off the master cylinder fluid reservoir? If not the fluid backing up to the cap will be slow to push past the vent.

you may have also got bad one ,that happens a lot on rebuilt or even new parts,unless there's back pressure holding it out ,it should release,another thing also, you should always replace those as a pair even though one seems to be good always do those in pairs,good luck.