Error upgrading to 3.0.1

Hello everyone,

I have a piwik installation which I just manually upgraded from 2.17.0 to 3.0.1.
Unfortunately, the update has somehow failed.

The update has been done manually, config file has been replaced, database upgrade using “console core:update” is done.

So we now have a 3.0.1 installation with a 3.0.1 database.
The webinterface throws the following error:
“Your piwik codebase is running the old version 2.17.0 and we have detected that your Piwik Database has already been upgrade to the newer version 3.0.1”

The codebase is most definitely 3.0.1, as verified by core/Version.php.

Logging in or doing other work is not possible.

PHP is 7.0.15, MySQL is 5.5.53, OS is Debian Jessie.

Thank you very much for your assistance.