Umm.. please always try to give as much information as possible when you are having problems. I don’t have a clue where to start figuring that out with your info..
What modx version, snippet version, snippet call, page cached, custom templates? etc...
"He can have a lollipop any time he wants to. That's what it means to be a programmer."
Once again I need to have my head examined. Solved it. Found I was following the Wiki tutorial to the letter and didn’t realise the the child gallery call didn’t use the embedtype that was called in the sub gallery itself.