The default CEEM (check external encryption mode) parameter is undocumented, and default of 0 makes behavior vendor-specific. The standard allows for a drive to report an error when trying to read a block that was pre-encrypted before written to the drive, such as is done with a keyless copy of a tape. This sounds like a very rare scenario to need to support. For the widest compatibility with data sources, this should be set to 1 for general-purpose use.