if you have the problem where alexa says "I found more than one device with the name (xyz). please give them unique names and run discovery again or create a group if you want to control them simultaneously" but you cannot find or delete the devices then I found a solution:

use the chrome browser plug called "alexa device manager". Alexa Device Manager

then once installed, go to "alexa.amazon.com" and click on the plug in and it lists ALL DEVICES, even the "ghost devices" that you normally can't delete!!!

Thanks for the info!