WiFi Adapter saying incorrect password after a few hours - OSX El Capitan

I have a Macbook Air with a WiFi adapter in it, I have tried two different brands, GYMLE and Edimax, both with the same results.

After a few hours, the WiFi adapters will just come up saying the incorrect password and discoect from the network, when the password is correct as it has been coected no problem for those few hours. I have also tried with WPS and get the same results.

Any ideas what is going on?. I would prefer to use the adapters as they coect at 780Mbits as opposed to 300Mbit with the inbuilt N wireless.

I have also formatted and reloaded everything onto it.

All its ruing is Plex, Calibre and VPN with an Orico RAID 5 enclosure and some exteal discs.

Thanks