I am testing loiter mode with optical flow

and after getting in to loiter about 10s with a little flow

my copter altitude oscillates and doesn’t get my RC command and throttle keeps go high and low which caused a crash

in the log I found ERR.FLIGHT_MODE-16 what is this?

here is my log

31 2000-01-02 오전 (1.3 MB)

and by the way is there a way to change log date,time with out gps?