I finally figured out what is happening on my 3Ps with the upgrade that had me puzzled from the start. I noticed that some voices were louder than others - but not always!

While playing a disco 'octave bass', I noticed that the higher note sounded a lot softer than the lower. I was playing in Poly 1 mode.

Then I switched to Unison 2, and I found it! The higher note would only sound softer if it used the same voice that previously played a lower note. Because in Unison all voices play, the effect is immediately obvious.

To replicate it:
- Switch to Unison mode (1 or 2)
- Play a LOW note first, and then a high note, f.e. G1 and then G2; the G2 will be quite a lot softer (about 6 dB).
- Play a HIGH note next and then the same G2; now the G2 will sound just as loud as the G1 and that higher note.
- It becomes most apparant from G2 and up, but it affects all keys.
- If you are in Poly mode, playing the same note 6 times will yield the same result to let each voice 'remember' the previously played note.

It looks as if some property that affects the VCA of each voice 'remembers' something which is not updated as a new note is played.
It is NOT dependant on Voice Mode. It occurs on both a Rev. B and a Rev. C 3P and is present since v1.0 through 1.5.3.