I have a strange situation. I have the house set as follows:

Surfboard Router (Bridge Mode) >> Deco X55 >> Ethernet Cable 100ft to Deco X55 (Outdoor Rated Cat 7 Cable Amazon) >> To PC.

Now I used to have My PC just go to the patch panel >>100 ft Cat7 cable >> Surfoard Router and I got  600+mbps.

If I hook it up like above it autonegotiates to 100mbps. I stuck a LinkRunner on the end and I can see it negotiate initially from a gig, blank out, 100mb, blank out, gig, and then finally settled on 100mbps.

I tested the long 100ft cable by itself with the LinkRunner and it reads as a Gigabit, then I tested the two smaller cables that terminate from this long outdoor cable and they both show Gigabit. I only speicfy all this becaseu I know people will immediately shout its your cablee but then how can that be if I can direct connect my PC to it and get 600 mbps? 

This is driving me nutes and I am starting to suspent the Amazon cable but then still go back to the ability to get 600mbps from the PC.