Have you tried change wireless channel? I think of course about main router settings

As a matter of fact I have. I also replaced the LP-Link extender with a brand new one.
The exact same problem happens.

The problem starts as following:
1. I plug in the TP-Link extender
2. I connect my pc by means of Wifi with the extender (Wifi network name ''TP-LINK_Extender_C10AD2")
3. I open my browser and start the setup to connect with my home network.
4. I pick region 'Netherlands' and choose ' next'
5. It says ' detecting the existing wireless networks' and a progress bar shows 0-100%
6. As soon as it hits 60%, the extender disconnects from my pc. After a few seconds, it pops back online and reconnects. In the meanwhile, my browser says it has been disconnected.

This new WA-850RE has the exact same problem as the one that has been replaced.

Any suggestions??

Funny thing is that it is not even connected to my home network before it starts disconnecting from my pc. Is there any way to change the channel of the extender itself? Couldn't find this option in the settings page..


-edit-

Using the back-button of my browser several times finally allowed me in the list of available wifi networks. I picked one and chose 'connect'.
A message was displayed that told me to wait for 2 minutes (to allow it to reboot). Now, almost 15 minutes later, it still hasn't gotten back online.
The only thing that I can do is reset it manually (with a paperclip in device itself). Then it is back to the 'TP-LINK_Extender_C10AD2' name and everything starts all over again.