If the Designer has ButtonEnabled=False (unchecked), the SwiftButton is displayed as if it were enabled, but user cannot click on it. The button needs to be repainted wrt ButtonEnabled when view is first displayed.
Wow, that was a fast reply. I posted the message then got up to make some tea. When I got back you had confirmed the problem and found a fix for it.
Now if only other software developers can work that fast I wouldn't have any computer problems at all.