Resolved
This issue was resolved this morning.
Update
This morning from approximately 10:00-10:15 PDT we experienced elevated error rates due to a very rare problem with our message queueing system. This issue affected a very small number of applications. Regardless, we have changes currently under development that should mitigate this problem should it recur. We expect those changes to be deployed within the next few weeks.
We apologize for the trouble.