@pbcd,

The first thing I would do is see what happens when you disconnect and reconnect your phone from the wireless network in that spot. If the strength of the signal increases there are a few settings that I would recommend changing to try and fix the strength.

You should also try to disable fast roaming and beamforming on your mesh network as I have seen these two , features be the biggest perpetrators. 

Disabling Fast Roaming will put your device in charge of switching bands and connections based on the signal strength, with Fast Roaming Enabled, the network will attempt to manage the connection with what it thinks will provide the best quality signal.

Your phones also have a feature for each network called Private Addressing, which provides the network with a random MAC address. While this is great for protecting your device when on public networks, this also prevents your network from identifying the devices that are trusted to be on the network and are used most often.