This makes sense - any operating system needs to properly unmount a volume (drive). The Tesla uses a Linux-Ubuntu OS so you must unmount a drive before removing it. And certainly MUST NOT yank a volume out when it's being written to. It seems that when the icon has the red dot it has opened a new file on the drive; if that file is not closed (by holding the button until the gray dot appears), the drive will be screwed up because that file pointer is not terminated. Anyway, in non-computer programmer speak, it makes sense that the drive must be unmounted (the gray dot) before powered down or removed. I experimented a bunch with this today and it seems correct. Just for reference I used an old USB thumb drive (1GB, USB2.0 protocol) formatted to MS-DOS (FAT 32) from a Mac. I do not think GPT format, new drive, capacity, partitions, 2.0/3.0 protocol or any of that matters. Hope this helps other M3 drivers. I love having the dash cam capability!