I get a speed drop after rebooting my Archer C4000.  In a minute or two the speed goes from about 940Mbs (I have a gig connection) to the mid 500's.  I have tested the speed with a direct connection to the modem and consistently get 900+.  I have a good gaming PC desktop with a wired connection and test with speedtest.com.  Wired through the modem, right after a reboot, I get full speed, generally 900+. 

Rewiring through the router, and freshly rebooted, I get 900+.  Waiting a few minutes, that speed drops to the mid 500's.  This happens consistently.  I know, it is selfish, but I want my Gig getting to the desktop.

Any ideas on what settings to look at?  The router is new, from Costco, thus I have some avenues for tech support.  What are the best options here at TP-Link?

TIA