We, too, have experienced similar issues. For starters, if we change the font to something like Courier, then find the need to change it back to regular, the font never looks the same as the original text. Your WYSIWYG has needed a refresh for some time now.
I've attached two screenshots where I changed the font and font size. It's impossible to change the font back to the original font and font size. I've tried a combination of all the fonts and sizes and it never resembles the original text.