Not quite sure what is bothering you however a couple of things could be involved.
Looking at your bottom picture it would appear to me that the turbulent flow that would be formed by the airbrake being extended could easily have some effect on the nearby aileron.
Also the basic roll damping of the wing could be changed by airbrake extension. The less efficient a wing is at producing lift is likely to reduce its natural roll damping. (Roll damping being due to a down going wing producing more lift thanks to the AoA increase and the upgoing one less lift - which naturally damps the roll).
Given that airbrakes are only used infrequently I would not expect the designers to compromise the basic aileron/roll rate design isues in order to counter an airbrake effect.
JF