I measured all envelopes outputs on the scope and they all work perfectly. With sustain at maximum, it goes to 8V.
The 6 envelopes all reach the 6 inputs on IC32 perfectly.
However, the multi env out, (IC32 pin 3) is very weird.
I have attached here the output from the scope. I simply trigger one note at a time with the hold button ON. So you can see the 6 envelopes accumulating, but some weird voltage shift appear at some point, and you can clearly see that the voltage on the first voices is half what it is at the input of IC32.