Whether it's a problem with the sizing die, undersized bullets, thin cases, ect., or a combination of the above, based on your description, its sounds like a case neck tension issue. Are you experiencing any bullet set back in any of your loads? It almost sounds like your bullets may be creeping forward under recoil, causing the problem rounds to be to long to feed properly, with some coming all the way out of the case.

Thing is, usually bullet creep forward is seen in revolvers, and bullet set back in autoloaders. But no matter what, any bullet moving around in the loaded case is a strong indication of neck tension problems.

While I don't personally like them, lots of guys do like the Lee Factory Crimp Die for making "problem" loads work. Might want to try one before you go thru the expense of replacing your other dies, brass and bullets trying to find a combo that works for you. As far as your bullet loosing .001 after being reloaded, this is common with soft bullets and taper crimp dies, especially if the bullet is measured at the base.

Larry