Please confirm if there is a bug with flexbox order in Firefox Developer?

Question

css

To begin with, I want to find out if this is a bug. I
made this slider https://codepen.io/casufi/pen/mONWry used flexbox to align the slides.
Relative positioning was done through flexbox order. It works fine in all browsers (IE Edge) but in Firefiox Developer 52.0a2 (2016-12-29) (64-bit) the order gets messed up when the first or last element is active.
1) Validate the behavior in Firefox 52
2) There are suggestions on how to make it more universal, I'll listen.
Swipe is done with the mouse left to right on the active slide

Answer 1

When loaded in Firefox beta, the order of the elements is the same as in Edge.
And in Dev Edition it is really different.