How heavy are they?
If the eclipse has a very light air system and barrel, then the difference in weight of the two markers would cause the kick. What about barrels? A long boomstick barrel will reduce the kick compared to a short ally freak for example. Otherwise, I can't suggest anything except that the only part to cause a reasonable kick will be actually fining the ball - do both markers fire the same velocity? are the bolt and firing times set the same on the boards?
Hope that helps, but sorry I have no definitive answer.
Tom