I could never get any netwrok speeds higher that 100Mbps with the AX1800 router, using my DIY CAT 5e and DIY CAT 6 ethernet cable. Here is what I tried:

• I removed my 70ft CAT 5e network cable fromt he wall and it still failed to give me 1Gbps speeds
• Check FW and HW updates and all was up to date
• Reset the router (no go)
• Setup QOS (still no go)
• I purchased new 100ft CAT 6 network cable and installed new RJ45 connectors and still no go
• I worked with TP Link Support and did not find a solution (I was told my router was passed the 2 year warranty period)
• I tested each wire with my multimeter and they each tested successfully (the cable was fine)
• I tested that each wire of the network cable was firmly connected via the vampire taps in the rj45 connector on each end of the cable
• Purchased another rounter and the problem followed (not the router)
• I worked with a frind of mine and he reminded me how the twisted pair wiring worked and I realized that the way I made the cable prevented me from getting the 1Gbps speeds
• I rewired the  network cable using the T-568B standard and BAM!!!!!!  the network cable was showing 100Mbps and now using all 8 wires
• Problem solved (for me at least)
• Hope this helps someone else