Edit - user was confused by the fact that subreddits on Old Reddit can have custom stylesheets. Extension is working as expected.

If you're having issues, please report a bug here - https://github.com/tom-james-watson/old-reddit-redirect.

I have never seen this happen and have no way of investigating this and fixing it if it's a real bug if I don't have a bug report where you can let me know what browser version, OS, other extensions you have etc.

Generally issues with the extension stem from it clashing with other extensions users have installed - so try disabling them and trying again.