simpleMqttBroker repeatedly drops off the network

[lutorm]

I'm running the simpleMqttBroker example, 2 clients are publishing and 2 are subscribing. After about 10 minutes, the broker consistently drops off the network. When this happens, I get the following on the serial port (with loglevel INFO):

[611318][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 0
[611324][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 0
[611330][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 0
[611337][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 0
[612183][I][MqttBroker.cpp:49] addNewMqttClient(): New client added: 3
[612190][I][NetworkClient.cpp:565] connected(): Unexpected: RES: 0, ERR: 0
[621452][W][NetworkClient.cpp:500] readBytes(): Timeout waiting for data on fd 51
[628198][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 3
[628204][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 3
[628211][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 3
[628217][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 3
[628673][I][MqttBroker.cpp:49] addNewMqttClient(): New client added: 4
[681453][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 2
[681459][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 2
[681466][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 2
[681472][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 2
[684282][I][MqttBroker.cpp:49] addNewMqttClient(): New client added: 5
[689739][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 1
[689745][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 1
[689752][I][FreeMqttClientTask.cpp:16] run(): Deleting client: 1
[689758][I][MqttBroker.cpp:55] deleteMqttClient(): Deleting client: 1
[690918][W][NewClientListenerTask.cpp:38] run(): Client from 192.168.1.144 rejected.

I guess the question is why it starts deleting clients... It always happens after about the same time.

Any suggestions for further troubleshooting?