Projects from Mpc500 to JJOS : Track mute issue !

Hi all,

Just wanted to find back my old projects of 500.
I switched of my 2500 from XL to Jjos1. works pretty good !
Except a strange problem with track mute.Some tracks doesnt want to unmute.
Are like freezed randomly depending of the project loaded. All the empty track are permanently muted too...
No way to even "listen" how its sounding but i can access to the step edit, listen the pads in program mode... But not unmute !
Of course, no track mute events recorded...

Anyone managed well transferred projects from 500 to big sisters ?

Thanks for help !

Tried few stuff more...
Copy a track in the same sequence make the same result. A track was stick muted is still mute on her copy.
Copying from seq edit mode, looks working. Just quite boring if i have to copy all tracks one by one and reassign all programs manually to make a new sequence...
Bug report ?