Dart actuator gets jammed

[Tomker]

Hi all,
We are having a major problem with our 6" dart actuator, we use it to raise and lower a shooting arm and are using its entire range of motion. Whenever we lower it to the bottom and have a little bit of force applied on it, it gets stuck and is not able to push back up. Even after we detach the dart from the arm and there is no pressure applied on it, it is unable to open itself.
We are able to spin it by hand but it is much harder than it should be when no force is applied on it.

The last time we had this happen to us we had to disassemble the dart pretty much completely and reassemble it in order to fix this lock and this does not seem like a valid solution especially since it's reoccurring

If anyone ever encountered this phenomenon or is having any idea as to what could cause it and how it could be fixed we are pretty desperate for a solution...

Thanks...