Well it seems that you are encountering the same problems with their dumpers probably the ink you use just blocking the whole yellow dumper, chinese dumpers does not work properly, I recommend you to use original dumpers.
I believe that you are not in trouble with the cable hardness, because if u have problem on this cable, the print head can not work properly. Also there could be trouble in oring, otherwise you'd be with leakage problems which by my understanding is not happening.
Hope this helps.
Sorry for my bad english!