Copter3.4-dev Crash (EKF_CHECK-2)

Hello,
I had a weird crash with my big camera X8 using 3.4-dev.
I had 4x 20min flights without any problem using 3.4-dev before. I used it because I needed the external Barometer…
I flew it in stabilize while suddenly it rolled to the left and crashed (EKF_CHECK-2 error appeared). The Logfile is attached…

https://drive.google.com/file/d/0B2P7_aBCn5tRNFpvTDB6M2Z4aTg/view?usp=sharing

Does no one have an idea what could have caused this crash?!

Hiya, looks like the same problem as people are having with 3.4 on the pixracer: