Seems to me there is an issue with the way the USB Source is saved and recalled in a show. Lets say you start out with the SQ-Drive selected. You recall a show in which USB B was saved as a Source. If you look in the I/O tab, the previous selected SQ-Drive is still selected. However, If you now ‘Go’ a scene, then look in the I/O tab it will change to the saved USB B Source , but it will not work ! In the I/O tab you have to manually first select SQ-Drive and than reselect the USB B Source , to get it to work.
Would be nice If this can be fixed. Thanks !