After upgrade 10.13 to 10.14ß7: can not login anymore

Hello,


i scanned to forum for similar issues but did not find anything helpful yet...so:


I just upgrade one of my machines (MacBook Pro 15", 2017) from 10.13.6 to the developer beta 7 of Mojave. Everything seemed fine, login screen came up. But whatever i try, i can not login. My password is not working anymore. I think, ok, maybe it's the heat or i've got a stroke or something and forgot or misremember or mistyped it. But i (double-, triple-) checked, i've got it in my password manager and could look it up. Tried a lot, did not work. I rebooted. Tried to reset the password. Even tried my filevault recovery key, doesn't work either. Nothing get's me into the machine. I can't even unlock the volume (tried password and recovery key) from single user boot. Always get a "Can not unlock that volume with that password...."(it's in german so I don't know what the correct english error message would be). Got only one account on that machine so i can't log in from another one...Of course i checked the keyboard-layout settings, but they are ok.


Never had something like that before. I'm using betas on different machines sinces ages and had some incomplete installations or something but never a complete lockout from an account.


Anything i've forgot to check, does anyone have an idea what i can try?



best,

alex