1995 Mazda B3000 Engine stops suddenly

Engine stops suddenly for no apparent reason - resulting in no spark & no fuel. But engine still cranks over and as soon as it happens it won't start. This truck is equipped with distributorless ignition

Twice its happened. The first time I changed the crank angle sensor, then the cam poition sensor and then the coil pack with known good ones. Cleaned the cables and other electrical connections. Gave up and had it towed to a local garage. Got it there and it started up and ran like a top - nobody touched the engine. The mechanics put their instruments on it and could find nothing wrong. Left it there for over a month trying to get to go wrong again. Gave up - it wouldn't go wrong so they could figure it out. Took it home and drove it for the next 3 months - no problem. Recently it stalled again on the highway - had it towed back to the same garage. Tried to start it at the garage - wouldn't start but ok turned over - left it there. Expected that it wouldn't start for mechanics next day. Next day mechanics tried to start it and it started immediately and they couldn't get it to not start so could not do a diagnostic.

A friend suggested the power supply to the computer may be faulty - ie poor connection or faulty fusible link - giving an intermittent connection from time to time. But it still cranks over when there is no spark or fuel supply. Any ideas?

One thing. The first time it wouldn't start was the next day after a very sloppy wet snow storm.
The second time was the day after a very rainy day.

Could the computer be getting wet - then drying out? How can we find out for sure without changing expensive parts like computers on spec?

Thanks, Ben Noble