Welcome to one of the biggest projects I have ever had, well, heaviest at least!. this thing is a monster of a generator for a hobbyist, probably weighs 2.5 metric tonnes, and it needs a lot of work.
Sadly it looks like a winding is burnt out, at first I though the errant reading was damaged or shorted wiring in the cabinet, but one armature winding is toast, but it may still output 2 phases that we can use. if not, I will keep the skid, engine and radiator, the rest can be scrapped.
How Delightfully Evil!
Always wear Eye and ear protection
Just remember, this is deadly power and should be treated with care!, disconnect and discharge before doing anything!