Do you use Fspassengers?

I had same thing, I was flying Fspassenger cargo flight with cargo 707 that was in really bad shape, I just bought cheapest one I could find, day before I tried same flight and my pressurization went off.

That flight was between Kabul and Kandahar airports, both in Afghanistan. When I had reached my cruising altitude I noticed that my electrical system had failed, but I continued to hand fly the aircraft towards my destination. Then when I descended I finally found out that I couldn't use spoilers and flaps at all, just managed to lower landing gear manually.

To make it all even worse some taliban went and shot one of my engines while on approach (FSPAX has war areas by default), so I had only 3 reversers available and runway was icy. I overran and my pilots got hurt, thankfully I got still my revenue from cargo and the crew got back into service after just few days in local hospital.

Somehow on at least CS 707 FSPAX electrical failure also causes these systems fail too, doesn't seem to be happen with other addons. I actually like it that way.  :D