Can update 3.A.0129.20210805 be rolled back by switching the OS slot?

Can somebody please check whether software update 3.A.0129.20210805 can be rolled back to the prior OS version before the update by switching the OS slot with fastboot?
I’m not running Fairphone OS currently, so I wouldn’t know.

For safety’s sake it would be better if somebody with confidence in their data backup and experience with the fastboot command would try this first.
So, assuming the phone is in Fastboot Mode and fastboot is working:

  • fastboot getvar current-slot … should result in a or b.
  • In case of afastboot --set-active=b
    In case of bfastboot --set-active=a
  • fastboot reboot

Some background:

Software update 3.A.0129.20210805 suffers from some bugs which cause a lot of grievance currently.

The Fairphone 3/3+ is a so-called A/B device. It has two slots for the OS (A and B). While you use one slot, updates get installed to the other slot in the background, the reboot in the updating process then simply boots the updated slot. User data is shared, it just stays in place.

This means after an update the OS state before the update is still there on the other slot and you can revert back to it.

In my understanding the procedure shouldn’t do anything to user data or to the installed OS versions.
In my understanding it should result in the prior OS version booting successfully as if the update didn’t happen (as long as the major Android version stays the same), the bootloader even does this automatically if it detects that rebooting after an update fails several times.
But I learned recently that switching the slot can also result in a prompt giving the user the choice to try booting again or to confirm to a factory reset (which should help with booting, but would delete user data), so I don’t want to just assume success. This prompt is kind of expected in case switching the slot results in an upgrade or downgrade of the major Android version, but in the /e/ forum has been seen while having the same major Android version, so I’m rather cautious about this.

After testing this the slot can be switched back to the 3.A.0129.20210805 slot to make the updated OS boot again.


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