EKF3 failsafe triggered when attempting GPS denied

Hello,

I was wondering if anyone else has had this issue. I have recently upgraded to ArduCopter V4.3.0 and attempted to fly with just a rangefinder enabled today. I have a GPS, optical flow sensor, and rangefinder connected. I have a switch for GPS disabled, radar on/off, and surface tracking. Once the rangefinder was the only switch on, I saw an EKF lane switch then a EKF failsafe was triggered and the drone attempted to land. Once GPS was turned back the the failsafe cleared.

Any help would be appreciated.

EKF3 landing
This is the messages I saw on the GCS.

As always: please post a .bin flight log.