Unsupported File Format Issue

Apparently i have an unsupported file somewhere in one of my projects. Every time I load the project the warning pops up, even if the unit is powered off and powered back on with that project (doesn't happen with other projects). The project is fully loaded, all 16 banks have 16 tracks filled. I've been through all of the banks and they all play so I'm not sure what the issue is here or how to go about locating the unsupported file. Anybody have this problem? Any info would be much appreciated.