There are many possible causes of this problem on the convertible Sebrings, the most common problems are as follows;
1) The cargo platform in the trunk is in the wrong position which blocks the rear window from folding downward. Ensure that the cargo platform is in the down position before attempting to operate the top.
2) The Hydraulic pump is low on fluid, it is located in the trunk, in the left rear corner, underneath the carpet. Inspect the fluid level in the reservoir.
3) There is an electrical fault in the system.
4) There is physical damage to one of the panel pivots, inspect for panel binding while the top is moving.
A couple questions for you;
When the top stops moving can you still hear the pump running or does it go quiet?
When the top stops moving does the cluster display "convertible top in operation" or "convertible top malfunction" or something else?
Report back with anything you find or if you need further help.
I’m happy to assist further over the phone at https://www.6ya.com/expert/nathan_cc888cf971f43e78