It's becoming a bit of a pain when views in the architect preview begin to cover over each other. I find it happens all the time with containers in a tab panel layout, where the content of tabs above show when I'm trying to view containers underneath it in the stacked structure.
Attached is a screenshot to show what I mean. In the example, the tab 'menu' is holding a navigation view. Stacked above it is the tab 'news' and the content of the primary view of that tab is showing through on my preview screen.
The bug appears when you hit the refresh css button.