Loiter mode,The plane is out of control

My plane fly in loiter mode,the plane fly good in the beginning ,suddenly the plane roll to 90 degree ,I Switch to FWBA mode ,save the plane .I check the log when I go back .I find some abnormity.
firmware : ArduPlane V4.2.3 (55685c43) ,maximun bank angle 45 degree ,I use Flaperon.

before 9:47:21,the roll follow desroll,and bank angle less than 45 degree ,it is normal .after 9:47:21,the different between roll and desroll is bigger and bigger ,rcout9 (aileron channel ) doesn’t seem to be the right response.why? the roll angle is more than maximum bank angle (45 degree),max to 90 degree ,I Switch to FWBA mode ,the plane over turn to normal . How is it happen?

I looked further into the log,when the plane roll is 45degree(maximun bank angle 45 degree) ,The throttle automatically increases to maximum,then the roll didn’t follow the desroll , Although the ailerons gradually increase,but the plane keep on roll ,max to 90 degree .The conclusion may be that you cannot add throttle to maximum ,when the plane circle at large angles . Help me analyze it!
my plane:


the first breakdown's  flight log link : 

the log is big , The breakdown occurred at 9:47:21.