It is WordPress security to remove backslash “” if you save or modify the theme stylesheet file in the WordPress editor making the font icons to be unusable. To fix this, you should re-install the theme, and if you need to modify the theme, use a child theme, and modify it offline or in your web server editor instead of WordPress editor.
This gives you pretty much the same outcome and works on every browser, and you don’t need to worry about it. For the other arrow icons, you can similar with v < > ^ and transform the scale when needed.