arduino_version dev
WiFi is not simple. I have a couple of different APs (from different manufacturers) I could connect to some are better than others (RSSI is pretty similar), with channels etc not conflicting.
I feel that it is probably an authentication issue with how the protocol is implemented on different devices.
One particular AP absolutely hates the old Android tablets I have - disconnects all the time, so I have a cheap TP-Link AP for those to connect to.