Vintage synths+ProTools Midi=chaos

[rjd2]

Hi folks. I am wondering if any of you have any insight into some tech issues I have been having with Protools and old synths.

I recently upgraded to a new Mac Studio with 2x UAD Apollo 16 interfaces, and 2x MOTU Express 128 MIDI interfaces. The MOTU units distribute MIDI to a number of vintage synths: OBXA, Prophet 5, Synthex, JP8, Rhodes Chroma, Memorymoog, T8, Juno 60, a few others. Some of these machines have factory midi, some have kenton or otherwise midi kits. I essentially ran this same rig on a 2015 iMac up until a few months ago, and while I experienced occasional "hung notes" via midi, the system was workable.

After rebuilding my midi studio on the new comp, I am seeing some very strange behavior on several synths when sending midi data to them. On the Prophet 5 for example, sending midi crashes the machine if I put it in loop mode, or hit play with the cursor at the start of the midi performance. It even bricked the entire patch memory. I have seen it cause the Chroma and MM to crash. The JP8 and Synthex have yet to go haywire.

I have turned off the MIDI beat clock function for all the machines, which did cause ALL of them to eat it. but i've checked my midi tracks for any data or info on the "program change", "sysex" etc view in Protools and theres nothing there. Is this anything someone else has experienced, or even heard of? I need to find a solution, and all the Protools folks have no insights on the AVID forums, so I figured I'd try it from the other angle. Thanks for any thoughts.

[cutoffres]

If you have not modified the midi files, i would suggest a MIDI filter that just let pass only notes, then check if it works like this. If yes let pass more MIDI events until it crash again.
Are you sure you've got one more machine since the last set up? All the machines connected in midi could had wrong events...
Simplify you MIDI set up to one or two machines to check if it works as it should, then add more machines until it crash. This way you will find where is the problem.
It also could be problem in MIDI settings on Pro tools.