Wired Connection Issues

To make things easier to explain I will provide some context.  We have a moden/router unit (xFi device for ease of reference) and my own personal router.  My personal router is connected to the xFi device.  The wireless capabilites work as intended and very rarely drop.  The wired connection however, seems to plauge my roommate.  At seemingly random times the connection will drop.  Sometimes multiple times during a single day.  We have tried switching ports on both the xFi device and my personal router but it doesn't fix the issue.  The cord is 50ft long, cat 7 cable.  Wireless isn't the best option for him since the connection slows dramatically.  Can someone please help us to either fix/understand what is happening and why?  I have tried searching for issues matching ours but to no avail.  Thank you very much for your time and assistance.