Eh, no one has suggested the most likely scenario...

Flaperon mixing with elevator to flap mix dialed in as well.

We have a number of planes larger than this on our field and they do the same thing.

It's not the servos.

Usually several servos are hooked together to act in unison, which in turn prohibits any servo chain from sagging.

Several of the pilots have elevator to flap mixing dialed in and their planes will look exactly the same way when the elevator stick is pushed forward.

If you look in the picture the ailerons are not at full travel as well.