Hi Florian,
I did find a work around. I discovered that if I unplug and then re-connect any piece of USB midi gear connected to the computer MT would start as normal. Not sure what that means, but it’s not a particularly difficult work around, there is a keyboard on the desk right in front of me so I just have to pull out and reconnect the USB on the back of it. The issue doesn’t exist on my laptop, so when I’m using MT for on site work it’s not a problem. I can open MT sessions created in the studio and everything works as expected.
Thanks for looking into it.
Dan