I purchased some Polar Camel mugs from JDS and I was going to engrave them with a logo from a test event my work just completed. I can't seem to get the mug to spin on the rotary attachment. It will start to spin and then it just falls off the rotary. I think the handle is too heavy for either the rotary motor or maybe it is too heavy for the amount of grip the rotary wheels can apply to it. Anyone ran into something like this before?