I've never, ever heard of this happening before. I put new SS lines and did a flush a few days ago, and today on the road at about 65, pedal to the floor. Thankfully I was able to stop and pull over to a side road and it wasn't really close or anything, but that's my biggest fear while driving lived out.
Obviously I didn't pull the bleeder valve out or anything when bleeding, just loosened it and then tightened it up again.
Has anyone else heard of this happening? Do I need to threadlock it?