Product and version (e.g. FileMaker Pro 14.0.3)
FileMaker Pro 17
OS and version
Mac, latest OS
A Custom Menu item that has previously had a script assigned to it will still run the script even when the Action is turned off.
How to replicate
Create a new file and a new menu. Add a Menu Item with no command specified, and check the "Action" box and assign a script that does something, eg a dialog. Duplicate the Menu Item and then de-activate the Action checkbox.
Enable that Menu set, and run both Menu Items. Both will perform the Script even though it was disabled in the second item.
There's also a serious DDR issue in that the script is retained in the Menu Item setup, but not reported in the DDR at all for the second item. We'd be able to pick up the issue if the step details were included, regardless of the state of the checkbox - it would be very handy to include the step in the DDR regardless.
Workaround (if any)
You cannot turn off the Action checkbox, you need to re-create the menu item from scratch, but that will also throw a "Script Not Found" error unless you either assigned a script or a Command. You must do one or the other or both, but the UI shouldn't allow you to leave the setup in such a badly configured state.