If it were me, I would try to setup an over the air pcap for the location
of the MacBooks and see if you can capture the drop off period.
Curious question, but we're they roaming (mobile) or stationary when this
occured? It sounds like the devices did a probe request and the AP did not
respond with the 802.1X network possibly. Strange that it would happen to
all at the same time. We're they all on the same AP?
Another question, have you checked the interference or noise? Possibly
noise could be causing lost frames from time to time and that lost frame
might be a probe response.
I think PCAP would be the best place to start if you can catch it happen.
Otherwise you can also monitor MGMT frames from the controller based on AP,
but I'd have to look up command, can't recall at the moment.