My mother has a 3rd gen Moto G that I bought for her, and she's having an issue with maintaining a constant connection to her Wifi access point (an Asus RT-N56U) in either 2.4GHz or 5GHz mode.

Now she's not losing connection to the actual AP, but she's getting the unhappy exclamation point, and it's not falling back to the cellular connection rapidly. I cannot reproduce this with my Nexus 6, nor my father's 2nd gen Moto E, but my sister's 1st Gen Moto E and my other sister's 2nd gen Moto G experience same issue.

Any clues on where to start tracking this issue down? The connection strength is strong, it's not losing comms on the air interface (Layer 1), it's losing comms somewhere beyond that.