The exception mentioned in this Rails issue, gets completely silenced by the Airbrake gem, making it impossible to catch and resolve: rails/rails#2509
The issue is currently holding back our production deploy.
I've created a project to demonstrate the issue: https://github.com/UnityTech/flash_bug
Thanks for creating the project I can recreate this issue with, it's making my life easier. :)
I'll check it out.