Okay, so I managed to get this working & to be honest it's difficult to tell exactly what it was I did which fixed the issue.
Basically, I had wrapped all my controls inside a main view in order to be able to apply a total height constraint to it. That view did have user interaction enabled, but it seems like it wasn't passing the events through for some reason.
In any case, I removed that wrapping view & everything is now working.
shrug