step 1 - ok 4,00VThis is the expected voltage for C6.
step 2 - 125,7mV instead 125,0mV potentiometer to the max
This means that when you play C1, the pitch will be too high (roughly by 10 cents).
The manual says you should not go above 0.1 %, that is 125,12 mV (corresponding roughly to 1.4 cents).
If this variable resistor is damaged, you should perhaps consider changing it.
You could first check it: once unsoldered, its total resistance should be 20 ohms.
step 3 - 125,1mV instead 125,1mV
If you meant 125,1 mV instead of 125,0 mV, that's within the tolerances.
step 4 - 131,4mV instead 132,4mV potentiometer to the max
This is 15 cents too low.
Increasing the voltage on TU to around 4,04V helps for step 4 but the others go south.
That's obviously not the way to go ;-) Keep TU to 4 V.
Anyway, fix the issues in the order of the steps.
