When AV500 plugs into AC1900, wireless connections on PC loses internet access

I just bought a AC1900 with DST adapter to replace my ASUS router.  First question, the DST adapter only gives me about 60Megs when my PC is connected to the gig port (PC has gigE interface), no where close to 1Gig bandwidth. What throughput should I expect over the ethernet connection of the DST adapater ?

I then tried using the Netgear AV500 powerline adapter with my AC1900 router. plugged the AV500 into one of the GigE ports on the AC1900 router; once plugged in, my PC that is connected via wireless loses its "Internet connection, even though it is still wirless connected to the network. When I unplug the AV500 from the AC1900, the internet connection is restored. Any idea what could be the issue ? Note: I had the powerline AV500 connected to the old ASUS router and it works without issues.

Calling Netgear support directly; they routed me to Bestbuy Geek Squad; but the Geek Squad was no help.

Thank-you.