SERVO_AUTO_TRIM Question AP 3.9. Ailerons fully deflected on landing

I have been flying a Nano Talon with the latest version of Arduplane and I have had a few good flights. I am using the SERVO_AUTO_TRIM = 1 feature. When I landed today after a flight with no apparent control issues at all I noticed that the plane has ailerons at maximum deflection yet I can see no logical reason for this. Is this normal? The trim on the aileron is actually almost at maximum (and it started the flight close to dead center). Conditions were not very windy and landing and approach were normal. It needs a proper tune but it flies decently.

There must be a logical reason for this but I cannot understand why. In case it is relevant I have included the log for the flight. My Mini Talon and Bixler have not shown this behavior.