Steps to reproduce: 1. Set up code that will immediately throw an exception on page load. 2. Enable "break on uncaught exceptions" 3. Reload to hit the breakpoint once. 4. Reload again to continue the debugger and immediately pause again. At (4), both the slide-in and slide-out animations will be active at the same time, leading the contents of two dashboards to be overlaid until the second animation finishes. I think this could be fixed by making sure to cancel/fast-forward any outstanding animations when starting a new one. The same sequence of events (without visual problems) seems to happen when going from breakpoint to breakpoint or stepping, but I believe there is a hysteresis/delay implemented for that case already.
<rdar://problem/19168653>