here's a good example for you:
I ripped open the right rear door today because it was not locking. (open and shut, but (surprise) no locking and the inside lock mechanism was jammed hard. AllDataDiy showed little about this. I looked at it, looked at AllDataDIY and still could not figure it out. I pull the three torx bolts from the lock and remove the handle rod fastener = the whole thing just comes out easy, but it took me 2 hours to look into it.
The solenoid (magnetic lever/switch) was jammed, I take the solenoid part off (2 parts: solenoid and all the lock crap) and try it out = now it works. I put the solenoid part on = lock now works fine. Put the lock back in = works fine. Eventually put the trim back on the door, but thought i may want to keep the trim off until I try it out for a few days.
A few hours later I noticed that now it is not locking correctly again. Better than before, but sometimes it won't lock. Eventually it does lock after cycling on/off a few times, but not all the time.
With the door it's not so bad because I can probably get the lock out in 10 minutes now. With a tranny you are looking at a weekend of work and the car is undriveable.