Yeah. As I alluded to earlier in the thread it was something they actively tried to prevent.
From a No. 6 Squadron report on 'S' guns during operations:
It was found that a number of aircraft were not opening fire simultaneously with both guns. Inspection revealed no fault in the solenoids or firing units but it was found that the rubber in the armoured hose was slightly defective. Being unable to expand outwards the rubber consequently expanded inwards, thereby reducing the passage for the air. Replacements of armoured hose are difficult to obtain, and it was found that by unscrewing the firing cylinder nut one turn and inserting a washer, the plunger did not quite bear on the tail of the trigger sear pawl and was therefore better able to overcome the inertia of the trigger system. It is therefore possible by this means to make an adjustment for small differences in the responsiveness of a pair of guns.
Also, from a bit detailing their training syllabus:
... To initiate pilots gently, they are sent up to 1,000 feet to fire the guns. Once semi-accustomed to the behaviour of their new weapon they are permitted to come down to 100 feet where the drop of the nose on firing is more apparent. An intentional stoppage was engineered on this practice to demonstrate the swing of the aircraft if only one gun fired.