DNN redirects to 503 error page instead of a 404 error page

Question

We have got two separate servers running DNN version 9.01.01.

They both are configured the same in IIS with Custom Error Pages turned off. The web.config is set to:

<customErrors mode="off"/>

We are trying to test and go to a page which does not exist which should give a 404 Error page but instead, it goes to a 503 Error Page (Service Unavailable). When I look at the DNN Admin Logs it says the that it is trying to go to a 404 error page.

I noticed that when I select a non-specified page in the DNN Settings under the Behaviour Tab, it then gives a different error:

From this information, I suspect it is a DNN 9.1.1 bug?

I found a previous bug which was present in earlier DNN versions: https://dnntracker.atlassian.net/browse/DNN-8611?jql=summary%20~%20%22503%20error%22%20OR%20description%20~%20%22503%20error%22%20ORDER%20BY%20lastViewed%20DESC

I also found this DNN post:

https://www.dnnsoftware.com/forums/threadid/538218/scope/posts/getting-503-error-instead-of-404-page

Answer 1

I actually figured this out. Remove any modules from the page that require user/session data. Best way to solve it is to remove all modules from your 404 page and start adding them back to see which one is the culprit.

Answer 2

I removed the 404 and 500 pages selected in Site Settings > Behaviour and deleted the pages. I re-created these pages and selected them again. The site will now show a 503 error instead of a 404 error. This is a DNN 9.01.01 bug. Upgrading will probably solve this issue.

https://www.dnnsoftware.com/forums/threadid/538218/scope/posts/getting-503-error-instead-of-404-page

Answer 3

I have upgraded to DNN 9.2.2 and still had the same problem.

I changed the Page Persistence setting to Page instead of Memory and it fixed the problem.

http://www.dnnsoftware.com/Content/Dnn.Platform/Documentation/Using%20the%20Control%20Panel/Host%20Console/Host%20Settings/Advanced%20Settings/Performance%20Settings/Setting%20Page%20State%20Persistence.html