This has been seen anywhere from 10-75% of the time with various decks when using SYNC I/O's 9-pin ports with Pro Tools 5.3 through 5.3.1cs2.Try increasing Preroll value and Minimum Sync Delay. For sessions with less than 24 tracks, try reducing the DAE playback buffer to 1. NOTE: Do not attempt this with larger sessions.If the above software adjustments do not resolve the issue, use a Keyspan USB to serial adapter rather than SYNC I/O's 9-pin ports for Machine Control. This will be resolved in a future version of Pro Tools and/or SYNC I/O firmware.