Aura ONE partly bricked Kobo Aura one

Hi there,

so, I "partly" broke my Aura One finally.
It still works, boots up fine, I even can read books....but:
I cannot install/uninstall NM any longer (as soon as i place the "uninstall" file in the directory, there's a "Import content; 6% done..." on the screen, and it freezes. I cannot install anything (tried to install KoboMail previously ( --> i think, that messed up something; tried to re-install NM, no success)
when i try to ssh into the reader, the connection is closed from the reader (port is open and i can connect (you can see it with ssh -vvv)), but it'll be closed eventually.

if i do a factory reset, the "remains" from NM and Kobo Mail are still there...
ah...i am on the latest FW - 4.38.23429

So, what option do i have left?
Is there a possibility to Re-format, re-image, re-<younameit> the aura one?

any ideas?