I have a single user that has admitted to having a really old Android phone. Throughout the day, he notices that he drops off WiFi and his phone will alert him there is no Internet, although still connected to WiFi. Again, this is just one user and this happens at all the locations that he works at. He is connecting to MR33s at all locations. No other Android or wireless users have noticed this. I see nothing in the logs to be able to troubleshoot. At one location, the AP is less than 10 feet from his desk. This just started when we moved to Meraki from ad-hoc Aruba networking.
I assume this will be driver related, what version of Android is the client running? You're not running any minimum bitrates on any of the SSID's are you?
The only other concrete way of troubleshooting would be to perform a monitor-mode packet capture when the client is associating to establish what is the underlying problem.
Usually, in this day and age, it is more cost effective and less stressful to replace a single device that is experiencing anomalous and difficult to isolate behaviour.
Time and time again I see people bird-dogging problems and a half-hour job ends up going on for days and days. Suddenly a half hour that can easily be absorbed by other projects becomes 10 hours of write off.