386.5 - webadmin username/password error after upgrade

[MeMeCe]

Hello, after upgrading my RT-AX68U from Merlin 386.4 to Merlin 386.5 I am not able to log into webadmin because of „username or passord error“. But I am pretty sure both are typed without any mistake, I had to log in couple of minutes before to run the update. The same problem when accessing the router from "ASUS Router" android app with saved username and passord. Also tried default username and password, byt without success. The router itself works fine. Any advices, please? Is there anyhing I can do besides reset and config from the scratch? :-( Thanks in advance.