I have no idea what I've done, but when I add activex buttons to my sheet I have to click each one twice. The first click it simply gets focus (it briefly gets the cross/navigation style icon) then it puts the focus dots round it.
I then click it again and it finally calls the click event.
It does it for brand new buttons I add too. Macro buttons are ok.
I spotted this, but no answers: Excel ActiveX after Windows scaling, Objects require an 'extra' click