I found a support knowledge base article that is relevant: https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS4393
The setting I was referring to is an "advanced setting" called pegraphicpi. If you set pegraphicpi=on then it won't send graphics. If you set pegraphicpi=off then it will send graphics.
I haven't tested but toggling that setting may be a quick way to determine where your problem lies.