My sister has acquired a Vax u87-zm-p upright that she says picks up perfectly but seems to suck itself to the carpet one second then as if it does nothing.
Gave it a try myself and it does seem to pull hard down of the carpet even when the height is adjusted to its highest. Then as if nothing.
Suggested it was a decent hoover and thats how it is? Can see it could be heavy going after a few minutes it pulls that well!
Is there a problem??
If you put the machine on it’s back turn the carpet height adjustment control and see if the wheels or base move allowing the machine to be further away from the carpet. If not the machine could be faulty.
Sadly there are very few parts available for that machine.