I'm not sure if I understand you question correctly but normally the these SEO settings are used to generate a 301 to the exiting page. So the issue you have is that some don't generate a 301?
BTW, if you would be unable to solve this, we have a module you place on the 404 page to do the same.
(seo redirect link in my footer)

Thanks for responding Timo.  It's good to know your redirect module exists.  I do use your Sytlehelper module. 1000 thank you's for that cool tool.  It saved me on several ocassions.  If you're ever in Oregon I will buy you a very large beer.

And yes many of the 301 redirects were not sending 301s.  They were sending 200 OK.  For example I set up a vanity URL /reformation500 to 301 to www.cui.edu/aboutcui/reformation500 but instead it sent a 200, showed the page at www.cui.edu/aboutcui/reformation500, and kept the URL as www.cui.edu/reformation500.  Basically it was acting as a Rewrite.

It took me a long time to figure this out but I solved it a few minutes ago.  As it turns out there is a hidden setting in TabSettings named "DoNotRedirect".  When that Setting has a Value of "True" any 301 set up on page settings does not 301 but rather acts as a Rewrite and sends a 200.  Crazy.  

I have no idea how this setting got set to "True".  I've looked all over Page Settings and there is nothing in the UI that I can find. So I did a db update, cleared cache, and voila - now we get proper 301s.

For those who come after me here are the steps to fix this issue:

Run the SQL update below (use at your own risk):

UPDATE [TabSettings]
SET [SettingValue] = 'False'
WHERE ([SettingName] = 'DoNotRedirect')

Clear the DNN cache under the gear icon >> Server >> Clear Cache

Clear your browser cache

Test and use a tool like https://websniffer.cc/ to verify that your URL is sending a 301 properly.

- Mark out

 

In the future, another troubleshooting step you can use for URL issues is to turn debugging on in DNN itself (not necessarily in the web.config, but that can help add even more information), and then also set Log4Net to log "All."  Then use a tool like the one you mentioned or Fiddler.  I haven't tried it recently, but in the past, doing this will add more troubleshooting details to the headers of the responses sent by DNN.  This helped save me hours of troubleshooting in the past.  :)