Going to be a difficult one to run down, but I'm 99% certain it's not flight model related. The reason I say this is that there is nothing in the FM which could give differential aileron in a left / right sense. There IS a table which adjusts the effect up and down, and for a brief moment I wondered if that had become 'altered' in the core game flight model. However, I fired up the Vulcan and see no issue - the extremity of each axis gives me a reading of 1.000 in the controls debug tool.