Hotpoint 7822A – slight clean water leak

This machine has a slight water leak from the lefthand side as you face the machine. After removal of the side panel that side, the source of the leak is obvious. It is from the roughly 8mm overflow hole that is provided (for some reason) about 20 cms up the right hand side of the transparent moulded set of reservoir tanks and siphon tubes that cover that side of the appliance.
To watch this working is a delight of which Rowland Emett would truly have been proud.
The little bucket-type switch works well and operates the microswitch OK. Water fills the reservoir until the top of the siphon tube is reached when then it empties out, cutting off the supply. There are three cycles of this and all is OK until the third cycle, when, I assume, because or the higher water level now in the machine, the water does not drain quite quickly enough into the machine and about 30 mls is ejected through the overflow aperture.

The filters in the base of the machine are clean. The pump seems to run OK – there is usually about 1.5 to 2 cms of water left in the filter at the end of a wahing cycle. The outlet tube appears to be clear and not obstructed.

From the ‘high tide’ marks on the transparent plastic moulding below the overfolw hole, it is obvious that the peak level has been rising gradually with time.

What component is failing that gives this problem please?

Peter