1GIG Speed last 3-4 days and then goes down to 95MBS.

First, none of the speed set for residential service is "static". It is shared among customers in the area and Cox says "up to" in their documentation of speed. Fiber has more bandwidth to share in the last mile of the connection, but it is still shared. You need Cox Business fiber for dedicated bandwidth/speed.

With that said, what speed do you get direct to the fiber modem/ONT? If it is bottlenecking at 95Mbps, it sounds like a ethernet problem either between the ONT and router or with the router itself.