Thanks a lot! This helps!
There seems to have been a mistake during production and one of the two wires on top of the Juno-66 is soldered in the wrong place.
We somehow must have missed this during testing..
This is most likely the cause of your problem.
Attached a picture, just move the wire to next pin as shown
I would also like to apologize for the troubles and the time you spent on this. I sent you a coupon code via mail..