When operating the cable slides, the in and out cable blocks pass by each other. Mine sometimes catch, but release. It could be yours is not releasing.
The reason they catch is because of poor installation. When tightening the cables, the cables have been twisted. The twist in the cable causes the block to rotate. Only when the blocks are vertical do they cleanly miss each other.
If you remove the facia board that is covering your motor, you can see the cables operate. That should give you clues on what is wrong.
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