Can't Assign a Button to a User Flex Phrase

Hello! Something seems to have changed with the latest update? I can add a Flex Phraser to the Program Tree, click ‘User’ and an editor opens up - I edit the phrase - all good. But then when I try to assign a button to it (‘Snapshot Variation’) it doesn’t trigger it. It lights the little orange bar to indicate the variation has been assigned, but pressing the button does nothing. It is the only Flex Phraser I have in the program tree, so the button is not being confused by any other open variations. I’m sure this used to work…