reset MT setup without deleting backup files (possible)?

Hi there.
I’m unable to login on one of my MT’s (both locally or remotely). Not sure if it’s a hack or config setup issue but MT had to be hard rebooted (pwr off / pwr on) since some of it features stopped working.
After a reboot all functions went back to normal (like vpn etc), though I’m unable to login. Same with using Winbox and MT’s MAC address…
I keep getting: ERROR: wrong username or password

I’m using Winbox only. It’s a slight chance that it’s trully a wrong credentials issue but I’ve already tried all of my known/remembered logins/passwords…

Since MT has loads of custom config restoring it from scratch would be a pain in %$#**
I have some ooold backup files but most of recent ones are on MT’s storage. Is there any chance to perform a config reset without loosing those files?

I’ve already tried using a reset button on a brand new MT with some setup backups stored, but after a reset those files are all gone.

have U ever tried connecting trough console?

Yup. Tried that yesterday. Had to make myself a console cable 1st. Anyway typing credentials doesn’t allow me to go further - I keep getting back to login prompt.
Any ideas?