Page Jumps when Dialog is shown

[jasonmng]

It's intermittent, not really sure what triggers it at the moment but when it happens the dialog will show but the page/body jumps down like 2-300 pixels first, then when I dismiss the model, the page jumps back up. I also observed this with the dropdown menu component. To fix the issue with DropdownMenu I had to set modal={false}. Any idea on what the cause is?