Turns out I had renamed a page, but forgot to update the Controller name and the View folder name to match the new page name. Once fixed, no help. After a while of searching I went to EPiServer Admin / Page Types and selected my page type. The page type had the following warning:
The purpose of this functionality is to prevent you accidentally from overwriting the database with an older version of the page type.(Source). There are a few suggestions on how to fix the issue when following the link. What I did on my part was to upgrade the code to be of version 1.1.1, after which the changes were reflected in the code.