First time I'm seeing this. we opened one up to clean it and there was a foam type insert loose. This is one of the new models. and they have them at the back of the motor at top of the body two foam inserts on both sides of the tigershark. I guess these help it float up to the surface. (see pic).
I was able to reattach it but not sure if the positioning was right and can't find a diagram showing these foam inserts and how to properly attach them.
anyone else had this problem?