Hi,
well I had that problem with Midi Sync for quiet a long time. I´m using 2 Electribes and one external tracker (renoise) on a second mac and it was really hard to get it at work.
First used Ableton as Master, but that was just not working right, I checked all of the sync option in live and it was working right (for the moment), but the next day I started live again everything was wrong, the electribe and the tracker were some ms out of sync.
So I decided to set Ableton as a slave and that way works right, cause Ableton corrects midi timing in real time and sets warp markers automatically as it corrects. However it works.
But you have to set a incoming delay value everytime in live cause there´s a bug I think, it never gets saved. But if you have it once, always type it in there.
You can hear that live always corrects timing as it runs, the delays are sometimes out of sync, so as you recorded everything switch external off and everything is tight again.
That`s the way it works for me.
cheers.
(the type is set to midi clock)