I think my BOs warped around a bit too. I'm not sure the invisible wall will solve the problem for sure, but it's just a suggestion that might help. In the mission I've been working on I've started to make liberal use of invisible walls to counter situations where BOs warp through. It's a very irritating problem in my mission because at several points there's a wall with a force field and you're supposed to assess the situation and then lower it, but the BOs can ruin it by jumping through and aggroing prematurely.

If I have a chance I can try playing through again with a Fraps recording going, and then upload it to Youtube.