This has nothing to do with "Put Hard Drives to Sleep"... Though a burner is a peripheral, it is not a hard drive.
Rather, Apple icon > System Preferences > CDs & DVDs > When you insert a Blu-ray > (Select IGNORE). [The OS default is: Ask what to do.]
The burn application is conflicting with the OS and taking control of the drive. So, your burn app receives a drive already in use conflict. Regardless, of what you select any burn attempt will fail.
When this particular conflict occurs between apps, it also seems to drop the BDR-208DBK from: System Report
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