Can not change fontsize in letter head (default 14)

Hi, I like to change the fontsize in my letter head. When I select de drop down list of the fontsize, it shows size 14 being ticked. However to select another size or scroll the drop down is not working.

I’m using Chrome browser.

Any ideas what goes wrong?

I found the issue. This functionality does not work in Chrome but it does work in Explorer.
I can live with that, for me case closed.