Speed tests arent going to give you much information troubleshooting WIFI. Try switching your wireless channel to 1, 6, or 11. Those are non over lapping and have the best chances of offering a stable connection in an active area. Hardwire as many devices as possible.
For WIFI intermittent issues try pinging your default gateway from a wireless device. If you're getting decent ping times and still have crappy connectivity it could indicate that the wireless isn't the issue albeit not a detailed or all inclusive test.
Also, suggest unplugging any devices such as microwaves and cordless phones and testing that way. A microwave thats failing can cause problems as those devices operate on the 2.4 spectrum.
This post was edited by Lethardus on Sep 16 2016 08:28pm