Px4flow, loiter can not fix position

when I use px4flow, loiter can not fix position with proper optical flow data shown in live data and logs. the firmware version is 3.5.1 and the ekf-gps-type has been set to 3.

Can you detail your setup and post logs please.

https://drive.google.com/uc?id=0B1dYoU9ATTLtbzNlSFVTb050MU0&export=download

https://drive.google.com/uc?id=0B1dYoU9ATTLtbzNlSFVTb050MU0&export=download

my log

they’re 95MB files - are you sure they’re your logs? I haven’t downloaded them as google drive won’t scan them.
What GCS software do you use (MissionPlanner, QGC, MAVProxy etc)?