The firmware released in April of 2016 should give you 600mbits over powerline. Mine is flashed and the web interface reports "1.2.8 Build 140401 Rel.50484n" (this is the version for Canada). The...

Try using tpPLC to rename the devices.

Is there a version of the wpa4220 for your outlet? You can buy those individually. It looks very similar to your Wi-Fi access point except there is no electrical passthrough.

It's a utility that shows you all adapters on the powerline network. You can download it from tp-link's support section.

Download tpPLC from the support page and run it on a computer with an Ethernet connection to the network. Watch to see if the adapters disappear. If so, the powerline network is getting disconnected....

If you have tpPLC up and one of the adapters disappears then it is the powerline network that is being interrupted. This should not really happen but there are reports that it does. Check the tp-link...