polyphony in max for live - release problem

Hello!

I build a little synth in MaxForLive, and I would like it polyphonic (great, isn't it?...)
But I have a problem about adsr and polyphony.

It's about the release :
When a note on (note B) is triggered before the end of the release period of the previous note (note A),
there is a variation in the level of the signal.
Ok, it's normal : release of note A + beginning of note B = it's louder when the note B is triggered
And theoretically, if I play this two notes (same velocity - same frequency) in a regular interval (a loop),
the variation of the signal should be the same each time a note is triggered.

The problem is this signal variation is irregular :
for example, I play a note (note X - no variation in frequency and velocity) in a regular interval (loop),
using live sequencer, and then I increase the release time,
(the note is triggered before the end of the release of the previous note),
it appears an irregular signal variation at the beginning of each note.

Sometime notes sound louder, sometime weaker, in an irregular period time :

X - X - X - X - X(+!) - X - X - X(-!) - X(+!) - X - X - (X-!) - X - X - X - X(+!) - (X-!) - etc...

I assume it comes from the way I build polyphony in my patch,
but I watched and read several tutorials about polyphony in Max, and I don't understand where I'm wrong.

I precise this level variation is between 1 and 2 dB (!), and increase with a high release period.

In attachment, you could find the patch I build.
If you could take a look and give me some tricks or ideas, it would be very helpful!
Thank you.

Louis