sagemcom fast 5688w internet going out or losing connection

I've had issues since the 16th day (December 23rd) of the 15 day trial. Initially the device was doing the constant "powering up" reset for seemingly no reason except it had a device connected attempt to use any bandwidth at all I.E. turning on my Xbox, connecting to wifi via phone. I called corporate tech support (joke) and they suggested exchanging it at my local store and it could be a defect (go figure) did that on the 26th of December. Since that day i have had nothing but strict NAT type issues even after troubleshooting the Xbox and the device (hard reset, choosing ports). I can't seem to figure out if this isn't the product I'm looking for or if I'm missing something because the rep at the local (non franchise store was they called it) said she has the same device and plays the same game on the same console with no issues and we live in the same town.. which seemed like a long shot but we discussed the game in depth and it seemed to check out. Any advice on a remedy or fix to this? I'm open to VPN's of things like that just want to know it'll work before i spend more money. Like everyone else mentioned it works amazing when it works..