If there is no failure and warning on aircraft related to this issue, this is likely the result of the aerodynamic phenomenon described here below and referred to in FCOM 3.03.18 P.5.
When the flaps start to extend while the speedbrakes are extended, the airflow around the wings transiently changed and this transient change is not exactly the same on both wings.
Model: Manufacturer:
First Issue Date: 16-SEP-2009 Last Publication Date: 15-OCT-2012
This transient lift asymmetry between left and right wings induces a slight roll movement.
This phenomenon is an inherent consequence of the aircraft aerodynamics and mechanical characteristics and used to be observed always in the same direction on one given aircraft.
This phenomenon was assessed during flight tests campaign and found operationally acceptable, as it affects neither the manoeuvrability nor the performances of the aircraft.
Note that same behaviour can also be reported when the speed brakes start to extend while the flaps are in configuration 1+F or 2.
In this scenario, no maintenance action is deemed necessary.