Hi Pikaya
I just replied to another thread here, explaining a bit how the plugin works, hopefully this will give you an idea what is going on and how the plugin works:
http://wordpress.org/support/topic/or-between-taxonomies-and-reset-button?replies=2
If you did a search within a tag and selected orange
(if this was a tag you had), the plugin would redirect the URL to something like:
www.yoursite.com/tag/orange
This should show you all entries tagged with wordpress. WordPress & your theme should already be able to display this properly.
If you disable the plugin, and go to http://www.yoursite.com/tag/orange you should still see the tag page with the correct results.
If you are still seeing strange results on this page, then it seems like there is something interfering with the way the tag template is working to give you strange results which isn’t to do with the plugin.
Try disabling your other plugins first to see if this affects the display of the tag page, if there are still problems, then try testing on a different theme (I always use the WordPress themes for development, 2013/2014 for example).
There is a possibility that your theme developer has implemented your tags/templates in a non-standard way which is causing this.
Let me know how you get on 🙂