After checking every single insert I have found that they all do the same thing in the exact same spot which leads me to believe it is a problem with the o-rings inside of the freak back. I even checked the inserts with some calipers and they really didn't seem to have thicker walls on any particular side.
I'll see if S.P. will send me some new o-rings and hopefully that will fix the problem.
I do really like this barrel system... I just want to start 'shooting darts' like everyone says they are with this thing.
Right now it's more like lawn darts.