I'm not able to replicate this behavior on our 16.0.6397 installation. I tested a setting from each card on that page, and the Save button enabled as expected each time. Is there perhaps another setting on the page preventing the Save button from going active?
In a previous version we had an issue where a page required a field to be filled out, but if it wasn't, you couldn't make any changes to the page. That is, the Save button wouldn't activate if you DID change something. However, there wasn't an error thrown on the field when you opened the page...
To see if this is the case, open the page then use your keyboard to Tab through each field. When you pass a required filed that isn't filled out, or filled out improperly, you'll see a red validation error display. Fix that issue and you should be good to go.