It is most likely because you have SEO enabled and you changed the title afterwards.
I will try to explain what is going on.
SEO is basically a "fake" URL rewrite to what the real single url really is.
So lets take this photo for example:
http://www.kmods.net/ps4/photo/NDg4YzQyNGNkN2Y5/geotest.htmlThe title on it is "geotest" and the store uses that in the URL for better search engine placement.
The random character/number is the encoded ID of that media.
So lets say a month later I decide to change the title to something else like "mytest". The store will now rewrite the URL to:
http://www.kmods.net/ps4/photo/NDg4YzQyNGNkN2Y5/mytest.htmlThe media ID is the same, but the ending changed, so technically it is a new url and the old url still works as well since SEO is turned on and both are being wrote to point to the actual page of:
http://www.kmods.net/ps4/media.details.php?mediaID=NDg4YzQyNGNkN2Y5Unfortunately there is no way around this when you are playing tricks with search engines and rewritting your URL's, you will just have to be certain you have the title you want on each media before importing them into the store.