Siemens TK76K573: coffee cycle interrupted

Hello
,We have a Siemens espresso machine model TK76K573
.

When we want to make a coffee/expresso, we have the following malfunction:
- The cycle starts-
The coffee is ground-
The water is pumped, heated and then sent to the "valve" (part 0543 / 00654842
)- The hot water is sent to the ground and compressed coffee ("passing group", part 0711 / 00741901)


...




but very quickly (1 to 2 seconds) the water is redirected (by the "valve") to the "tank" (part 0113 / 00704177) via the "Recipient" (part 0529 / 00647106) and the cycle stops.

We initially thought that the "valve" or the "passage group" was defective. These two parts were successively changed without result.

In addition, to help with the diagnosis
:- When the "hot water" or "milk frother" program is selected, it works correctly-
The fault arrived gradually

.

At first it was one coffee out of 10, then one out of 2-3 and finally it stopped working.

We suspect a defect in the control board (aging / failing / out of order electronic component) but given the price of the board and the parts already changed unnecessarily, help/advice from someone who may have encountered the same malfunction would be welcome.

Thanks in advance for your help.