Help for MOTOR 2.2 Kw and control board optimum BF46 milling machine

[EddyCurrent]

Agree with Web Goblin,
3. A small amount of oil would not be of much concern, but obviously better without it, it's the oil seal that is suspect. It may also be that it's the gearbox at fault, maybe it lost oil during transportation and that oil has not been topped up.
4. It sounds like the circuitry on top might have something to do with speed or position feedback.
Web Goblin is talking the stator, the rotor you mentioned is the rotating part in the middle and in an ac induction motor would be extremely robust, look like a solid lump of metal with laminations, and unlikely to be a problem, though joints on the end of the cage have been known to fail.