OK, let me guess you have two devices sharing the Netgear over the mains adapter. My bet would be that if you check the ARP table on one of the TP-Link connected PC's (cmd screen, enter "arp -a") you will find multiple IP's with the same MAC address, and those will be the PCs and other devices connected to the Netgear. Checking the OUI (first six digits of the MAC that identify the manufacturer) will probably tell you whether it's the Mains adapter or Netgear that's eating your lunch (my bet is the Mains adapter). You'll probably find the same thing going the other way. The problem is that many mains adapters and some wireless bridges transport only a single MAC address across the link - their own. This allows any one device on the far end to communicate just fine, but since all traffic on the local LAN is addressed by MAC, not IP address, exactly which device is communicating at any specific time becomes undefined. Generally it's whoever spoke last. Which can get really confusing to most protocols. The solution here would be to set your Netgear back to being a router and using it's WAN port over the mains adapter - which means your now routed devices will use the Router's MAC to get across the link, and the router can figure out what goes where locally. This is unfortunate because it splits your LAN in half, with different IP addresses on both sides. You probably want to turn off NAT on the Netgear too, especially if you have need to access things on that net from the other, like file shares or printers. It's adding a lot of complexity, but it should solve your problem.