The mix of realtracks and midifiles was playing in sync in biab, but when I drag and drop this files in realband they was out of sync. I notice that by default the realband has a 120 tempo setting, and the files I was working with i biab was 114.
It seems like realband handles the realtrack and midifile different when the tempo setting in realband and biab are different, so the result is out of sync when playing. I now adjust the tempo setting in realband to the same as in biab BEFORE drag&drop a mix of realtracks/midifiles, and everything is ok

Thank you for comments

roger