Electrolux ES1 6104 – No water supplied to rotors

Hello all,
We have the electrolux model above, & recently it has an intermittant fault – there is sometimes no water supplied to the rotors which eventually we notice due to the smell of the powder being heated up.
If we leave it overnight it sometimes works in the morning, but not always.
Cleaning the filters does not appear to fix the problem.
Any advice will be much appreciated.
Thanks,
Mike