On hAP ax3, Router OS 7.6:
/system/reset-configuration keep-users=yes
After this, the password is reset to the one printed on the pull-out tab. I find this very annoying. Is this behavior done on purpose?
In the past, keep-users would keep the old password.
Have you tried to create a new user, admin was not meant to be really used, the first thing you should do is to create a user for you and delete admin, if you do that, does it work as expected?
I would say it is a good thing admin password gets changed.
It is the default entry for attackers.
Especially since it is set back to the one on the label, it requires physical access to the device.
As suggested, create a new user with full access. What happens then with that user ? It should work.