Padding crashing service studio

I'm having a strange problem. In my theme I've got the 'Blank Screen' defined as 'Layout_Normal'. I can create a new page and look at it in the browser without any problem, the issue comes when I try to open that Web Screen in service studio, as soon as I try service studio crashes. I eventually tracked down the problem, it's to do with some CSS on a container in the 'Layout_Normal' web block. The container had the following CSS - 


When I eventually removed this line I could then open the screen without it crashing. Any idea why this padding would be a problem? As I mentioned the screen renders fine in the browser.
I suggest to submit feedback to technical support if you have not done that already :)