I have two external USB optical drives, both burners, one that will work with DVDs and CDs, the other that will also handle BDs (Blu-ray Discs). I use these sometimes with MakeMKV. Recently I had an issue with reading a BD with MakeMKV and had to force-quit MakeMKV. I tried to eject the BD, but Disk Utilities would not because it was in use. (I remember at one point I found a way to still eject it, but I was unable to use that drive to read anything until I rebooted because the OS still saw it as in use.) I rebooted.
On reboot the OS recognized the BD in the drive and it came up in Finder. But I still heard a fair amount of activity from the drive. It's no longer making noise, but the access LED on the drive is still flashing. I've had this happen before, where I have discs in either drive, usually DVDs or BDs, and I hear movement in the drive even when I haven't been using any software to access that drive for hours or even a day or more. So it seems that something is accessing my external USB optical drives even when I'm not using any software to do this.
How can I find out what program is trying to access discs in my optical drive?