Can I change the Boot Slot from Fastboot with a command?

fastboot change slot   Dan fastboot get active slot

First you need the actual fastboot, 3 Then the correct command is: fastboot --set-active=a

If you device randomly got stuck in fastboot after a reboot, that means the counter hit zero and the bootloader marked your slot as unbootable  I guess your bootloader is unlocked? Did you try to change the active slot? Get the current active boot slot: fastboot getvar current-slot

open slot artinya stack trace: Error: failed to set active slot: Error: {error:{code:1,cmd:fastboot --set-active=b},stderr: waiting for any device > --slot SLOT Override the default behavior and prompt fastboot to flash the slot that is passed in as an argument --set-active