just an update,
This problem was solved for me by the support team of meta slider.
the fix is to add this line of code at the very end of wp-content/plugins/ml-slider-pro/assets/metaslider/admin,css
html[dir=’rtl’] .metaslider.metaslider_themeEditor .wrap {
position: inherit;
}
this fix is for version 1.2.2 of the pro version.
if you have a later version , this bug may already been fixed.