WAP4 wifi issues

Good day,I have a few WAP4 with some wifi issues.

Some find networks, selects the network and connects, however when it switches off and you switch it back on, it fails to connect.

others, you try and find wlans and it does nothing.

I have tried reloading the OS, CE6.0 and still nothing, does anyone have any suggestions, or maybe if you have the fusion files for WAP4 I can try that .

Regards

Andrew