Slider with jQuery UI not working properly in Safari

Slider with jQuery UI not working properly in Safari

I created an image slider where I use the jQueryUI draggable function and am experiencing a problem now with Safari. 

In Safari the following happens: on mousedown on a picture and the mouse is slightly moved the first image is moved in the visible area (doesn't matter which image was visible before) but on mouseup the next/previous image is shown (as is should). I don't really know where it comes from - maybe from jQuery UI draggable?

Here is a demo:  http://codepen.io/anon/pen/YXVmEm (the problem only occurs in Safari)

Here I have a question on stackexchange but unfortunately no response yet:  http://stackoverflow.com/questions/30741976/slider-with-jquery-ui-not-working-properly-in-safari