Your Joomla Backend template is problematic. There is a jQuery Conflict problem caused by scrollspy() plugin (i don't know what that plugin is though).
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The "Validation" works based on AJAX loading, since the jQuery is problematic the AJAX loading wasn't running.
I fixed the problem by temporarily changing the Backend Template from Isis to Hathor from Template Manager.. Then validated the Fancy Slider Module and then got back to Isis again. Since, you don't need to validate again, you will be good to go. But keep this in mind. you can fix it by the same method if ever you have to (by the way, i just noticed, the default Joomla backend template name is ISIS.. what a bad name, unfortunate coincidence ;))