Just to ask the question and trying to pinpoint this, what happens if the restrictions on these pages are removed (temporaily), do the pages redirect as expected?

If this can be tested on a DXP enviornment, do any errors show in the passportal? Or debug this locally where errors can be logged/tracked

Hello ZZ,

I believe the Geta Notfound Handler only actions it's redirect logic if it is a legitimate 404 error e.g. Content does not exist.  In your case the error is a 401 error at which point you'll need to add your own handler logic around users without permissions.