I am very happy you mention this, as I have exactly the same phenomenon in my L-39.

At first, I thought it is because of slow processor speed somewhere (which Weatronic confirmed could not be the case), but now that I read your post, I realize I have gyros on ALL three axis, and it might be simply caused because of the gyros (one dual axis GY352 and one single axis GY351).
I have reported this to Weatronic since I could notice it with my extremely fast servos (Futaba brushless BLS451's everywhere except flaps and valves) when rapidly moving around with the sticks.

Must say, it held me back for a while but I have flown again, and the pulses are so short that actually I could not notice it whatsoever in actual flight and now I do not worry about it any longer.

Nicolas.