Hello,
Could you clarify, what do you mean by acts as a switch?
Also, did I understand correctly, after each consecutive reboot, router boots with a different configuration/mode(switch->default->correct config)?
I suggest to create a backup of your current configuration by navigating to System -> Administration -> Backup and try to update the device to this firmware with Keep settings option disabled. If that does not help, you will be able to revert by downloading firmware file from here and upload the backup.
Best regards,
Žygimantas