This is turning into a case worthy of Sherlock Holmes. My MIDI signal from my MIDI controller, a Yamaha Motif XS8 connected via Firewire, continues to randomly disappear for no apparent reason. Internal MIDI, say playing a VI from a MIDI track inside Pro Tools, isn’t affected at all. It appears to be the Firewire MIDI.

I’m on a PC, running Win-10 Pro, 64bit. 

When I first turn on the PC, all MIDI is fine.  Motif editor works fine.  Motif works fine as controller for my Pro Tools tracks.

If I leave the PC idle for a while, and come back, the MIDI connection seems to have disappeared and the only way to get it back is to reboot the PC.

I’ve triple checked that I have installed the latest FW driver, including uninstalling and reinstalling it.

Checked all cable connections
Made sure all PC sleep/hibernate modes were off (Win-10)

It is not necessarily Pro Tools related as the problem will occur whether or not I’m using Pro Tools.  Its happened using Reason and Reaper as well.

A new twist popped up last night. All the MIDI was working fine. I created a MIDI track in Pro Tools and then wanted that track to play a patch on the Motif which I recorded onto a PT audio track. No problem. All worked per normal. Then, I spent about 1/2 hour doing some mixing/arranging with the session which didn’t involve me using the Motif as MIDI controller at all. Then I wanted to use the Motif to play a new part with a VI on a PT instrument track and the MIDI was gone again. Just, poof...gone! Can’t use Motif to play a VI and there’s no MIDI out from PT to the Motif either.

I’m at a complete loss here as to what to check, look for, try or anything else. Suggestions? Ideas? Should I call a priest? Anyone?