Copied that pic from sams post
It should be connected to the BLUE neutral not the live.
The metal shaft will probably be connected direct to the black, could be a choke though and this will discharge any stray static or live etc to neutral - as no earth on the cable.
Seen it myself, but never delved any further and nothing to worry about.
There is a stripdown thread on that model by beko which will confirm it goes to the blue.
If this machine has ever been rewired by anyone, then be careful they haven't done it incorrectly. DO NOT DISCONNECT THE BLACK
if you ever had a cable live fault shorting to the metal then it would be better for the vac to short to neutral and trip your consumer unit or blow a fuse - if you disconnect the black and it gets a fault, it could kill you.