In article 31f486ec-3d6a-44ff-b930-05ddc9b4d376
@s8g2000prg.googlegroups.com, says...
Before I shout at the supplier, has anyone any ideas why after use and
being empty (dry), it will gradually fill up with water even when
powered down.

Flake of scale in the solenoid valve. Take it apart and fettle it, or
replace with one scrounged from a dead machine.
--
Skipweasel.
Never knowingly understood.