The 283 build of Vegas Movie Studio HD Platinum 11.0 appears to me to have introduced a new failure mode where an event is duplicated on top of itself on the same track. If you try to slide it, you see the other version staying put underneath, and it seems to have crossfading between the two copies. Weird. Your suggestion to just select and delete the top layer seems to solve the problem. It’s not clear to me just what circumstances cause this to happen to an event.