Jason is correct, no shock in that.

You need for the rotary bolt to engage on the barrels more heavily on the left side of the barrel extension. If it bares more upon the right side of the extension the rotary bolt wants to turn and the top lever moves to the right. I have seen this several times myself and when fitting new fox barrels I always make the left side bare more heavily and they do not pop open when fit in that manner.

Jason has fit up enough rotary bolt barrels that he understands the mechanics involved.