Button malfunction - only part of the button is clickable

I've just had a similar problem on a complex diagram. I've had this one before. I sat and watched learners and the problems they were encountering. If they clicked a button and nothing happened their behaviour immediately changed and they went searching for other solutions on the screen. Even though the instructions were clear. After clicking lots of other things, they came back to the same button. They expected (based on other interactions) that clicking is reliable, so they were very unlikely to try different parts of the button.

My solution: I found that the arrow object has a very wide area of influence. If an arrow is near a button (e.g. 10px away) the cursor will turn from a hand to a pointer and the button stops operating. The solution was to move the arrow further away and bring the button into the foreground.

I've previously reported problems with arrows having a disproportional influence, but it seems I'm a lone voice.