Hi Adam – unfortunately I did not find the exact position but deleted all files from my server, set up a new wordpress installation connected it to my old database and did the rest through backups.
The only thing that seems to be obvious is that the redirect info is not stored in the database itself – seems to be somewhere in the plugin directory or even in the wordpress core. Also make sure to empty your browser cache or better restart your computer after any done chances.
Sorry that I could not help more.
Good luck!