We are seeing the same thing that Samuel Wolf described, but from our web UI and with 7.0.28-4+deb7u10. We get seemingly random 400 HTTP returns.
We downgraded to 7.0.28-4+deb7u4 and that problem went away. Unfortunately in our environment the Tomcat-side Java exception is not being logged, so we have some more digging to do. We do see the 400 error in the access log though.
