Temporary fix is to comment the code below line 209 - 215 of jquery.flip.js

      if (options.axis !== undefined || options.reverse !== undefined){
        changeSettings.call(this,options,function(){
          $dom.trigger('flip:change');
          if (callback !== undefined){
            callback.call(this);
          }
        });
      }

I do not see drawback to this (probably because I have a very simple usage of the plugin).

What's going on here is that the element has already been instantiated and its being called as if to change some settings but no settings have been provided. The error message is a bit confusing though. What was your expected outcome? Perhaps you meant .flip("toggle");?

Taking a guess at how your application is structured here, it seems you've got a bunch of blog posts elements that you instantiate at some earlier point, you load some new ones, and then you try the above piece of code to instantiate them all. The problem with that is that you're trying to instantiate the old ones again, and thus you get this error. This actually shouldn't stop all the new elements from being instantiated and should have no effect on the old ones, so i would imagine everything actually works as you need it to. But it's messy and you should probably make sure that you only try to instantiate newly created elements.

There is an issue here of flip not giving a clear enough error message in this case though, so i'll add a clear error message in the next release.

Should be fixed in release v1.0.16.