As they have drawn a new neutral wire and tested it yesterday, we need to eliminate that possibility now.What if the neutral is poor? I'm not an electrical engineer and am genuinely looking for some light on this. @zero7, Do you have something to talk about this?
@Love4sound ,is it possible that there is a faulty UPS somewhere in the building. If it's leaking to ground, that might be causing the high voltage. You can turn of the mains for the entire building for few minutes and check the voltage between ground and neutral.