@thijz: What your logs seem to show is a couple of instances of jumping between two APs on the same network. That's the only cause I see of disconnecting from a BSSID. I'm not familiar enough with wpa_supplicant to know what criteria it uses for switching, presumably something to do with signal strength, but the logs aren't really showing any data about the scan results to let us compare between the APs.
@thijz: What your logs seem to show is a couple of instances of jumping between two APs on the same network. That's the only cause I see of disconnecting from a BSSID. I'm not familiar enough with wpa_supplicant to know what criteria it uses for switching, presumably something to do with signal strength, but the logs aren't really showing any data about the scan results to let us compare between the APs.