I just purchased the Arris Surfboard SBG8300 and I am experiencing the same issues. Truth be told, the modem is a depreciable piece of junk. I had a TP-Link router connected with standard ethernet and never experienced a drop. In fact, never thought about the thing after I plugged it in. Like you, I called both support networks only to listen to each push the blame to the other. That told me they were full-of-it, so I'm going to figure this problem out myself. Once I develop a feasible solution I'll share it with the community.