I forgot to add, This occured on two of four cameras. It only happens when there is fast motion. On one camera it's when a drummer gets fast, on the other it isn't as bad and is when a guitarist gets a bit over animated.

The other two were on a pretty still keyboard player and some reasonably still singers. They were ok.

This is what's making me think it's a cheap camera thing.

Hopefully some confirmation or advice will help.

David.