I don't build pickups, only rewind them when needed. My first step after documenting all pertinent data is to carefully check the winding ends where they reach the eyelets. I would guess that 25% of all dead ones have issues there, making repairing a fairly simple job.
The P-Bass pickup shows signs of sweat/water/humidity corrosion. It may be too far gone to fix and may need to be completely rebuilt.
Have you tried taking resistance readings from the magnets to the lead wires? Sometimes that will show you where the problems are.