I’m in bridge mode and have the OOL Gateway Wifi disabled. If you have them do it I’m not sure what that looks like. I have the GR140DGM which I assume is the first revision of their gateway so my not apply to yours. I disabled the WiFi by holding down the info button IIRC, I just looked on reddit and found it below since I did it over two years ago and it survives firmware updates, power losses and reboots.
If you’re not sure if it’s coming from your Gateway or a neighbor and you’re running windows download WifinfoView from www.nirsoft.net, it will show all the AP’s out there. You’ll see hidden and unhidden AP's and some manufacturers and some Model numbers. You'll see all the mac address and PHY Types. You should be able to narrow it down from there.