If I add a user group to the 'deny' or 'grant' list in the CMS permission management of a site tree page and then save this it works fine. However if I edit the CMS permissions again and want to remove the group from that list again, this does not work. There is no 'x' icon to click on to remove the group from the list.
It seems that this is only an issue within the site tree. In the datamanager permission management it works as expected.