Added a gallery replacement success message and a reminder that you have to refresh your browser page in order to "see" the "new preview image" as your browser cache will show you the old one until you force it to update itself.
Also I'm adding a wait delay between file replacements.
This is due to members making multiple replacements in a row, I think they are trying to get their screen to update.
I'm assuming they can't read the "success message" or refuse to believe it but none the less for whatever reason the gallery will not let you replace a file more often than once every two hours at this point.
If this does not stop the problem then I'll make the delay longer until it does.
If you replace a file and want to see if it has been updated then "Download" it, don't rely on the preview to confirm it.
If the downloaded version is correct then guess what--the file updated, no matter what your screen shows you.