When MakeMKV detects the bug it tries to use a workaround specified in preferences. The same command for DVD discs is implemented correctly. Per both SCSI MMC and AACS specifications this command shall have no data payload but OS X driver requires non-zero data buffer. Two functions - IOSCSIMultimediaCommandsDevice::REPORT_KEY_V2 and IOSCSIMultimediaCommandsDevice::SEND_KEY_V2 in IOSCSIArchitectureModelFamily / IOSCSIMultimediaCommands / SCSIMultimediaCommands.cpp have the same error that prevents sending INVALIDATE_AGID command to a Blu-ray drive. Apple has been notified about this bug but apparently ignored it.
The bug prohibits release of a system resource so in a worst case you'll have to shut down and power on after opening every single Blu-ray disc. The API has a bug in it that prevents its usage without workarounds, and for small subset of drives there is no workaround at all. So, at least in theory, any program can read data and key material from Blu-ray discs without obtaining exclusive disc access and from any capable drive. Mac OS X version 10.5 "Leopard" and above support Blu-ray discs and feature API for Blu-ray specific AACS key exchange. A separate rant on this matter can be found here. Mac OS X version 10.4 "Tiger" and below don't provide any Blu-ray API and MakeMKV has to use so-called "direct access" API that works only with write-capable drives and is significantly slower compared to regular read access. DASPI kernel extension is included with MakeMKV. Starting with version 1.6.4 MakeMKV introduces DASPI disc access mode that is faster and more stable than "OS access" mode. NOTE: The text below applies only to "OS access mode".
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