I think it is a lot more than 1 in 5000. The first Televue EP I bought was a brand new 19mm Panoptic. It would not accept a nebula filter that worked fine on all other EPs I tried it on. Bintel sent me a replacement straight away, which worked fine. I heard from another member who experienced the same problem with a Televue EP.
I had the same issue with a 24mm panoptic I had bought from OS.
The dealer took a bit of convincing but eventually came to the party and shipped me a replacement barrel.
Seems to be fairly common and if i ever buy any more TV eyepieces new I will asking the dealer to check for this before shipping.