Using Octoprint from Raspberry Pi or connected directly to my computer using USB will give me a communication error after a short time & the printer stops. Printing directly from the SD card does not cause my printer to stop. Unless there is a problem on the USB connection on my computer & raspberry the problem looks like it points to somewhere in the USB circuitry of the arduino. Is that logic not correct? I have also tried 2 different USB ports on my computer with the same problem. Is there some Ethernet shield that I could attach to the arduino mega instead of using the USB connection?