It works on the demo site. I also workes on the site on the provider-server but not on my localhost. I made a copy of the server (files and database) on my pc and still the same behavior.
I attached a screendump.
Left the behavior on my local pc. If i change the font the dropdownbox keeps displaying "Font Size". When changing the font size I got a extra line but fontsize doesn't change in the editor/preview, the html code is correct "<p><span style="font-size: 36pt;"></span>test</p>" Right on the server the dropdown changes to 36 pt. Editor/preview the size is correct. The code is also correct "<p><span style="font-size: 36pt;"></span>test</p>"