If you use the openform statement and include either “nobuttons”,“yes” or “titlebar”,“no” as one of the options you will end up with an open form that can not be closed! The Close Window menu item is grayed out and a closewindow in a procedure is ignored. This leaves you in a nasty position because even if you hit the escape key to go into graphics mode there is still no way to close the window. Unless this is another problem related to the latest Sierra 10.12.1 release it should be addressed. This has been entered into Bitbucket as issue #615.
This is not Sierra-related. I get the same result in Yosemite.