Issue with powering off an MK brand 32A MCB
The handle moving to a central position is typically indicative of it having tripped and tripping when moving to Off, although not normal, is not unheard of. The part about this that is unacceptable is that it is not actually disconnecting when it does that. Regardless of whether you move the handle to Off or the breaker trips, it needs to disconnect and isolate. If your's is not doing that, it is seriously defective and needs immediate replacement.