Killing Dist pickups ?

The Ohm meter test in pickup is not very good. If it measures open, pickup is bad from broke wire or connection. One turn to turn short will fail a pickup, but cannot be measured, it will not stand out from all the other turns. The single turn short is like shorting output of a transformer, it hogs all the generated signal. Only a scope knows for sure. :)

As Del says, the connectors are not reliable. They are unsealed, and temperature cycles results loss of contact pressure.
Cleaning, tighten female contact by plier squeeze, and deoxIT may work. Buying new, gives half new contacts, may work for awhile, sounds like your problem.