Chrome: 56, 57
OS: Windows 10.1

1. Launch two chrome://md-settings tabs nearly simultaneously (example processes: middle-click a bookmark twice; open two settings windows one after the other, close them both, then hit Ctrl+Shift+T twice)
2. Wait

Expected: The pages load.
Actual: The pages spin indefinitely. The tab's title is right ("Settings") but the page is entirely blank.

The DevTools timeline shows that all activity just stops after a couple hundred milliseconds... no loading, scripting, rendering, painting. All (or at least a lot) of the resources appear to be loaded. No CPU usage.

Polymer.telemetry shows a few dozen registrations; sometimes it gets further than other times.

The DOM just has an empty <settings-ui></settings-ui> -- it's not registered.

Reloading the tab does the same thing, even if the second tab has been closed. Opening a new Settings tab does the same thing too. You have to close *all* MD Settings tabs before loading MD Settings will work again.