DHCP is the most important thing to check first, for a number of reasons. If a zero client's IP address changes, it must drop and re-associate to the host, causing the station to reset. This happens more often than you would think - yes, most of the time a client will get the same IP back. However, some locations do not, and address space exhaustion is very common in environments with public WiFi access. Zero clients that have to share a subnet with such things are not going to be stable.