During disc acceleration or when a drive encounters bad and unreadable sectors, it gets into a state, that freezes the program accessing it.
On top of that, all other programs trying to access the disc drive get stuck, until the disc drives show response again, or until the ejection button is pressed.
However, due to the SCSI response code "IN PROCESS OF GETTING READY", this effect does not occur during the initial reading after inserting the disc.
For older drives, it is even worse: GDR8162B may never unfreeze, until next power outage, if it gets stuck too long.
The state, where the disc drive is having hiccups. I wonder, whether it has names.
Why did the designers of SCSi allow "Erroneous read requests might take a long time to complete" (IsoBuster error message when deadlocked/bottlenecked by this horrible SCSI flaw.)?.
They should not have introduced annoying bottlenecks to SCSI.