Eslr9c lincat commercial cooker

Don’t normally touch commercial but this is a local pub with new landladies with what seemed like a bog standard fault.
Unfortunately I’ve never worked on 3 phase before and am trying to pick up as this call lingers on.
Initially one of the fan motor had blown, order motor and replace. Then second old fan motor blew……coincidence., then first new fan motor goes and now no coincidence.
Testing on the mains block I initially got, from the neutral up, 230v on each pair. Ok, checked all wiring (v. Helpful these comm. manufacturers, sent me the wiring diagram) and went back to mains block…..now getting 83v, 409v,336v.
The only difference between this v. basic cooker and domestic one is the contactor.
Any ideas guys…..flummoxed unless it’s a supply fault as lincat man says it could be a reversed neutral