Hello,
You could try to connect to the device via CLI/SSH and try the following command: /sbin/wifi reload
Did you have this issue with previous firmware?
Did you perform firmware update recently with Keep settings option enabled?
Could you try to reset the router to factory defaults?
If the issue persists, could you attach a troubleshoot file to your question. Please, replicate the issue, then access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there.
Best regards,
