You have a
Edimax wifi extender that was working and has become erratic. Is it still inside the warranty period?
Extends the range of existing 802.11b/g/n Wi-Fi networks
iQ Setup for easy Wi-Fi extension Smart 3-in-1 mode: Access Point, Wi-Fi Extender and Wi-Fi Bridge Finds best setup location for optimal Wi-Fi coverage with signal strength LED Compact, wall plug design for convenient placement
Features a hardware WPS (Wi-Fi Protected Setup)
Personally I have spent a lot of time ding research on "Wi-Fi range engenders" and have some ideas.
These devices are not suitable for all scenarios.
These devices may reduce the reliability of a home network.
You should make every effort to contact the vendor or the maker of the device.
Are all the devices in your home network compatible with the latest standards? Namely, the N standard.
http://www.webopedia.com/TERM/8/802_11.html