Actually, the suggestion is basically that if the servo isn't securely mounted, it's sensible to do something to secure them better.

It's really simple to see if you have that problem. Grab the aileron and hold it so it can't deflect. Move your aileron stick on the TX. This will not only show you if the servo is solid, but it'll also let you feel if there is any slop and where it is. You can feel or see if the clevises are loose on the rod, in the horns, or if the servo gears are not tight or whatever...........

If all the connections and gears are tight, and the servo flexes, check out why. Are they taped down? tape giving? Or is what they're attached to flexing? If so......... stiffen the structure around the servo..... etc etc

edit..... oh wait, I just looked at your pictures again and noticed the servos are screwed down. whatever.........