In TPControl we now report any ICSP related errors, and although the error states "System License Error", the error is in fact not related to the BYOD license. The error number "3" or "4" is an error which relates to an ICSP file transfer operation being already in progress. AMX restricts ICSP file transfers (which are used in the BYOD connection process) to one single transfer at any time. i.e. if a device is retrieving the BYOD file, then another device connects and attempted to do the same while the original ICSP transfer is still active, will result in the error. I would suggest also the error may result from a poor/disconnected connection during a transfer, and the AMX Connection Manager may hold that ICSP transfer open for a timeout period, even though the device is no longer connected. This timeout could be up to 2 minutes.
Generally, once you have successfully retrieved the BYOD file from the system (only needs to happen once), then you are less likely to see the problem occur.