Wiring for door speaker

[lonesailor]

I have an intermittent problem with the passenger side woofer going silent, I have established that the speaker itself is OK, but it sometimes ceases to work. Opening and closing the door sometimes fixes it so, so as I have proven that the output is OK and I have continuity in the wires, when I checked them at least. I assume a short to earth in the wiring. I have had the radio and the speaker out and have tried to pull the wires but they appear to be well stuck. Has anyone had this trouble and worked out how to free them, I could easily pull some new ones through if I could get them moving.