The fact that the icon is not rendering correctly on some browsers might be caused by the server restriction when it comes using the font icons. We have an article regarding this regarding the Font Awesome icon possible server related issues which might be the case. So please follow the steps mentioned here.
Please kindly consider that the request was originally a customization one and it was outside of our support scope. We did our best to help you out on the matter and whatever side effect the code is given might have or it may cause in the future cannot be in the support scope either.