What I gave you should output the paths and stop and not continue to load any page on the site.
The only explanation I have for this is that you are adding the filter after the hook has already run.
You said that this is in your functions.php so I assumed it was added at the right time.
However, it could be that something else is causing a premature initialization of ACF which can cause the hook to run before expected.
You need to disable other plugins and maybe switch theme to narrow down what is causing the issue.
