The best lesson I ever learnt was when fault finding, particularly in the relay logic age, was the best tool to fix lifts was your eyes. Understand your lifts, understand the general sequence of operation with the relays, and you will fix(or at least know where the problem is) most things within the first 5 minutes. This applies here, as if there is a generator problem you will see it when watching the lift motor run. You will even pick up the sound of an error from the other side of the room.

None,
All the peers give you good advice.
By my experience, check your mg or motor netrual. A lot of time mechanic change brushes and move the holder without knowing it.

You never mentioned if there was a load on the car or not. if any load, and if it has load weighing or not, most of them do. Check ECD,FCD contacts, (empty car down, full car down) They change your generator field.