Latency between Max and Pro tools

Hi there !

In my patch (simplified to the maximum), I send a midi note, from Protools to Max.
Midi play in protools > Max midi bus > Max software.

This midi note send a bang to a play object (a short sound like a metronome), this sound goes to a bus output (here dolby renderer), to go back to protools be recorded in it.

Protools Buffer : 128

Max Buffer : 32, overdrive Checked

I'm around 100 samples latency for this loop., between midi note and audio recorded. I wonder if i can reduce latency with a magic trick or does it seems normal to you ?
And second question, a bit weirder : each time I record, latency is not the same, sometime less 70-80 samples, to 120 samples approx. Seems random. Does it mean something.
Dolby driver should be stable. as it is made to sync to go forth and back between Protools and Dolby renderer...

I've tested with "Protools bus 1-6", stil the same issue.

Is there a way / good practice to sample accurate sync two softwares ? Both are in the same mac, so I thought I shouldn't have to sync them, but it creates doubts in me.


Many thanks for reading me, if you have any thoughts or idea, I would be happy to have your feedback.

Cheers