WiFi Near Far Interference?
WiFi channel 0 and channel 4 overlap slightly so interference is theoretically possible.
Channel 1, 6 and 11 are the only channel that can be used interference free from one another (you can look at this picture from Wikipedia).
That said, there are many other possible causes of interference e.g. Bluetooth, Microwaves usw. or the AP might just be to far away.