USB preventing boot up

[cliffyk]

AFAIK - the USB ports on all Elegoo printers are type 2.0--sometimes 3.0 devices will work with a 2.0 port, sometimes they do not. Your Saturn is likely attempting to read the drive during its boot process, perhaps even before the firmware has been loaded to RAM.

It's not a good idea to power up with the flash drive installed anyway, start-up transients in the power supply could wipe the data, or even damage the card...