I am trying to control some areas on a page type to a specific user group (Editor).

I'm doing this by editing the defaults page for the the page type > Clicking on the area, then permissions > Adding the group Editors > Selecting desired permissions.

Sometimes this works but often it does not. For example on one page type restricting Editors to add only 1 type of block works, exact same settings for an area on another page type will not work.

This seems random and flakey behaviour, I just can't work it out! Any advice please?

Also is it possible to restrict a usergroup to adding specific types of blocks on a sitewide basis rather than having to select each area?