Electronic control units generally work or don’t work but there are several types which can have different problems.

There are the button pad type which is where the electronic dosing and boiler fill is controlled from the button pad, the second is where the control unit is a separate box only controlling the boiler fill and the third type is where the boiler fill and the dosing is controlled from a separate box.

I’m sure there are others as now we have PID control units as well.

Faults.

For control unit’s that only control the boiler fill or your problem is with boiler filling please see Coffee machine overfilling and flooding.

If the measurement of the coffee is inconsistent then the problem lies with the flow meter the device the tells the control unit how much water has passed through to the group head, this is not a definitive diagnosis as I suspect the control unit can forget how to count but I doubt it.

Most flow meters have a small LED light you will see flashing, if it’s not flashing when calling for coffee then it’s not working, however if it is flashing and you have inconsistent shots it is the Flow meter not providing the control unit with the correct count.

If one side or one group head stops working where there is a separate control unit the key/button pads can be exchanged for each other to eliminate a faulty key/button pad, if the fault then swaps over to the other side then the key/button pad is at fault, if not then a new control unit is required.