Is it possible to stop strange URL duplication?

Hello I will try to explain my question... For example this is a URL for the latest post in this forum at a moment

http://www.mintjoomla.com/support/community-forum/user-item/4656-giorgi625/48-cobalt-8/7360-problem-with-record-rating.html

If we change a part of this URL from /48-cobalt-8/ to /48000-cobalt-8/ we didn't see error 404? Why?

http://www.mintjoomla.com/support/community-forum/user-item/4656-giorgi625/48000-cobalt-8/7360-problem-with-record-rating.html

same for users part of url

http://www.mintjoomla.com/support/community-forum/user-item/4656ASDASD-giorgi625/48000-cobalt-8/7360-problem-with-record-rating.html

Ok, I understand that we have a right canonical link for botj of this wrong url, but maybe is a solution to stop it