The issue you're describing is rather strange. It only impacts master board I-4. But what is really weird is that it only happens when one of the last four preset selectors is pressed.
The trigger wire is certainly not the problem since the other presets work with this board.
Did you try modifying the panel settings while playing board I-4, just to see if it's bound to a specific parameter of the synthesis line ? The first idea that comes to mind is that you inadvertently modified an other variable resistor while applying the tuning procedure. You could also make a thorough comparison with board I-3 for instance.
