Hi Serkan,
I made a mistake. It was not Opera mini, it was Opera mobile v.34. The same happens with the most recent version 35.
The same browser gives that erratic behaviour of simple gallery.
I have swapped first two margin values so the issue is solved for me.
/* SHORTCODES PAGE */
.show-buttons .button {
margin: 1em 0 1em 0;
}
instead of
margin: 0 1em 1em 0;