PT mtc jerky ?

[Aquarius]

Hi,

Following my tests trying to sync externally an mpc drum machine to Pt, I found mtc is not very rock solid.
In my setup, I used mtc out from sync I/O in mpc.
I've also tried using my emagic unitor mk2 out into mpc with same results.
For me, mtc was as solid as ltc meaning if both machines are set correctly with right frame rate and tempo infos, when Pt acts as a master, the other device should follow with no drifting and be right on the bar grids.
So what is happening here ?
When printing a simple 4 on the floor kick in Pt and checking it against the internal click, there is some delay between the bar grid and the kick transient.
This lag is not consistent...
What do you think guys ?
Cheers,
A

Pt hd 8.03cs2
Sync I/o latest software revision
G5 2x2.5
6g ram
Mpc jjos xl 1.41