Funny thing happened to me last night, I was playing around with the spring on the end cap. My battery was loose, so Sir Lawrence had told me to pull slightly on it so it would make the battery snug. Well last night I was placing a fresh battery in when I noticed the rubberised lining that the spring attaches to was sort of popped out on one side. I pushed the lining back in and gave the spring another little pull, I noticed it was a bit crooked to one side but thought nothing of it. When I screwed in the battery the saber started firing on its own. Pulled the battery out and pushed it back in, same thing firing on its own. I took the end cap off. Straightened the spring and put it back on and its not doing it any more. You might check to see that your battery is in straight and not touching any parts it shouldn't. This might be a reason for the firing that you all might have. This could have been caused by either fiddling with the spring or battery being loose.
Anyway, I hope this is quick fix for you both. Im sure if you all contact Sir Lawrence he might go thru the basic things to check and if you have a faulty end cap maybe you can either replace it if you Saber is still under warranty or buy a new one.