I was having a problem with a pulse sensor library and OS 5.3.0 (separately detailed here) and I found that I could downgrade the firmware to OS 5.0.1 as workaround.
In my class, I had students download the 5.0.1 bin, go to DFU mode, flash the firmware from CLI, and hit reset. For most of the students, it worked perfectly and the Argon had OS 5.0.1
For 4 students though, after they downgraded to 5.0.1 and hit reset, the Argon automatically updated back to 5.3.0. I tried the process many times, but each time after flashing, it would upgrade firmware again.
I’m really stuck and confused. Am I missing something as to why some Argons update after pressing reset?
The most likely reason is that the user firmware on the device targeted Device OS 5.3.0. If you didn’t downgrade the user firmware or flash tinker when downgrading, the device would immediately upgrade Device OS to match the user firmware version at boot.
Incidentally, how did you downgrade the devices? Changing the Device OS target does not downgrade the device. The target is the minimum Device OS that can be used to run the firmware. If the device has a newer version of Device OS it will never be downgraded OTA.