I hit an issue where I could no longer boot any of my CM4 modules in device mode from my Mac. This was particularly annoying as I had previously booted all of them to update firmware and write the OS. Every so often one of the devices would boot past "bootcode.bin" but more often than not I would get: Failed control transfer (-7,24) Failed to write correct length, returned -7 I tried different populations of boards and boards in different slots (knowing they previously worked) - to no avail. Then I realised I had "balena etcher" still running which I was using to write the OS. I closed the app and device booting worked consistently. I now see that balena must have been probing the USB bus for new storage devices causing the boot process to work. But I though I would point this oiut in case it helps anyone.

That's good to know. Thank you for the tip!

Noted. This is something that is easily overlooked and could result in rage quitting.