Now it's working again, which is good!
I shutdown Engen, then I turned all the lights on using the minimote (which worked without Engen). Still returned errors. But kept the server running and eventually the devices all returned and responded.
I think I caught the moment in the log when the devices and server started communicating again as expected. Hope this all helps, not sure what the error is here or if it was specific to something odd in my network.
I sent an email a full copy of the logfile.
2017-01-26 18:21:08: zdriver.0:Unexpected response: [13 00]
2017-01-26 18:21:38: zdriver.0:Unexpected response: [13 00]
2017-01-26 18:22:08: api:WebSocket closed.
...
2017-01-26 18:22:17: tornado.access:304 GET /assets/fonts/fontawesome-webfont.woff2?v=4.7.0 (::1) 5.00ms
2017-01-26 18:22:17: tornado.access:200 GET /api/v1/scenes?_=1485476536741 (::1) 6.00ms
2017-01-26 18:22:17: api:WebSocket opened.
2017-01-26 18:22:17: tornado.access:304 GET /assets/js/setup.js (::1) 11.00ms
2017-01-26 18:22:17: tornado.access:200 GET /api/v1/nodes?_=1485476536742 (::1) 39.00ms
2017-01-26 18:23:20: termserver:Starting
2017-01-26 18:23:20: zdriver.0:Started: COM3
2017-01-26 18:23:23: ztree:get 0:13/protocol => {'specific_type': 'power_switch_multilevel', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_multilevel', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:23: rest:Web server starting: http://127.0.0.1:52125 and https://127.0.0.1:52126
2017-01-26 18:23:23: ztree:get 0:14/protocol => {'specific_type': 'portable_remote_controller', 'cap': 18, 'basic_type': 'controller', 'generic_type': 'generic_controller', 'listening': False, 'sensor250': False, 'security': 22, 'sensor1000': False}
2017-01-26 18:23:23: ztree:get 0:2/protocol => {'specific_type': 'power_switch_multilevel', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_multilevel', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:23: ztree:get 0:3/protocol => {'specific_type': 'power_switch_multilevel', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_multilevel', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:24: ztree:get 0:4/protocol => {'specific_type': 'power_switch_binary', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_binary', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:24: ztree:get 0:5/protocol => {'specific_type': 'power_switch_multilevel', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_multilevel', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:24: ztree:get 0:6/protocol => {'specific_type': 'power_switch_multilevel', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_multilevel', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:24: ztree:get 0:8/protocol => {'specific_type': 'power_switch_binary', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_binary', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:24: ztree:get 0:10/protocol => {'specific_type': 'power_switch_binary', 'cap': 83, 'basic_type': 'routing_slave', 'generic_type': 'switch_binary', 'listening': True, 'sensor250': False, 'security': 28, 'sensor1000': False}
2017-01-26 18:23:27: ztree:probe 0:5/node_info => {'times': {'ack': 1, 'reply': 154, 'response': 11, 'wait': 0}, 'error': 'nak'}
2017-01-26 18:23:29: ztree:probe 0:6/node_info => {'status': 'ok', 'times': {'ack': 0, 'reply': 23, 'response': 6, 'wait': 50}}
2017-01-26 18:23:29: ztree:get 0:6/meter_supported => {'reset': 1, 'meter': 'electric', 'scales': ['kWh', 'W']}
2017-01-26 18:23:30: ztree:get 0:6/association/1/nodes => {'nodes': [40, 1, 194, 195, 38]}
2017-01-26 18:23:30: ztree:get 0:6/association/3/nodes => {'nodes': [4, 3, 139]}
2017-01-26 18:23:30: ztree:get 0:6/association/2/nodes => {'nodes': [65, 2, 14, 6, 49]}
2017-01-26 18:23:30: ztree:get 0:6/association/5/nodes => {'nodes': [175]}
2017-01-26 18:23:30: ztree:get 0:6/association/4/nodes => {'nodes': [9, 3, 47]}
2017-01-26 18:23:30: ztree:get 0:8/meter_supported => {'reset': 1, 'meter': 'electric', 'scales': ['kWh', 'W', 'V', 'A']}
2017-01-26 18:23:31: ztree:probe 0:8/node_info => {'status': 'ok', 'times': {'ack': 2, 'reply': 29, 'response': 8, 'wait': 47}}
2017-01-26 18:23:32: ztree:get 0:10/meter_supported => {'reset': 1, 'meter': 'electric', 'scales': ['kWh', 'W', 'V', 'A']}
2017-01-26 18:23:33: ztree:probe 0:10/node_info => {'status': 'ok', 'times': {'ack': 9, 'reply': 75, 'response': 9, 'wait': 48}}
2017-01-26 18:23:40: ztree:probe 0:13/node_info => {'status': 'ok', 'times': {'ack': 0, 'reply': 23, 'response': 6, 'wait': 52}}
2017-01-26 18:23:42: ztree:probe 0:2/node_info => {'status': 'ok', 'times': {'ack': 0, 'reply': 23, 'response': 6, 'wait': 52}}
2017-01-26 18:23:43: ztree:probe 0:3/node_info => {'status': 'ok', 'times': {'ack': 1, 'reply': 24, 'response': 7, 'wait': 52}}
2017-01-26 18:23:44: ztree:get 0:4/meter_supported => {'reset': 1, 'meter': 'electric', 'scales': ['kWh', 'W', 'V', 'A']}
2017-01-26 18:23:45: ztree:probe 0:4/node_info => {'status': 'ok', 'times': {'ack': 0, 'reply': 26, 'response': 6, 'wait': 47}}
2017-01-26 18:23:46: ztree:get 0:6/color/blue => {'value': 0}
2017-01-26 18:23:46: ztree:get 0:6/color/warm_white => {'value': 0}
2017-01-26 18:23:46: ztree:get 0:6/color/green => {'value': 27}
2017-01-26 18:23:46: ztree:get 0:6/color/red => {'value': 27}
2017-01-26 18:23:46: ztree:get 0:6/meter => {'scale': 'kWh', 'precision': 2, 'value': 234, 'rate': 'import', 'meter': 'electric', 'size': 4}
2017-01-26 18:23:46: ztree:report 0:6/sensor_multilevel/power => {'scale': 'W', 'precision': 1, 'value': 1.4, 'size': 2}
2017-01-26 18:23:47: ztree:get 0:6/1/basic => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:6/3/basic => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:6/5/basic => {'value': 0}
2017-01-26 18:23:47: ztree:get 0:6/4/basic => {'value': 0}
2017-01-26 18:23:47: ztree:get 0:6/basic => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:6/2/basic => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:8/color/blue => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:8/color/green => {'value': 255}
2017-01-26 18:23:47: ztree:get 0:8/color/red => {'value': 11}
2017-01-26 18:23:47: ztree:get 0:8/meter => {'scale': 'kWh', 'precision': 3, 'value': 4477, 'rate': 'import', 'meter': 'electric', 'previous_value': 4477, 'size': 4}
2017-01-26 18:23:47: ztree:get 0:8/basic => {'value': 100}
2017-01-26 18:23:48: ztree:get 0:10/color/blue => {'value': 5}
2017-01-26 18:23:48: ztree:get 0:10/color/green => {'value': 197}
2017-01-26 18:23:48: ztree:get 0:10/color/red => {'value': 255}
2017-01-26 18:23:48: ztree:get 0:10/meter => {'scale': 'kWh', 'precision': 3, 'value': 8194, 'rate': 'import', 'meter': 'electric', 'previous_value': 8194, 'size': 4}
2017-01-26 18:23:48: ztree:get 0:10/basic => {'value': 100}
2017-01-26 18:23:48: ztree:get 0:13/basic => {'value': 99}
2017-01-26 18:23:48: ztree:get 0:2/color/blue => {'value': 0}
2017-01-26 18:23:48: ztree:get 0:2/color/cold_white => {'value': 0}
2017-01-26 18:23:48: ztree:get 0:2/color/warm_white => {'value': 0}
2017-01-26 18:23:48: ztree:get 0:2/color/green => {'value': 255}
2017-01-26 18:23:48: ztree:get 0:2/color/red => {'value': 255}
2017-01-26 18:23:48: ztree:get 0:2/basic => {'value': 99}
2017-01-26 18:23:49: ztree:get 0:3/basic => {'value': 99}
2017-01-26 18:23:49: ztree:get 0:4/color/blue => {'value': 0}
2017-01-26 18:23:49: ztree:get 0:4/color/green => {'value': 0}
2017-01-26 18:23:49: ztree:get 0:4/color/red => {'value': 0}
2017-01-26 18:23:49: ztree:get 0:4/meter => {'scale': 'kWh', 'precision': 3, 'value': 33846, 'rate': 'import', 'meter': 'electric', 'previous_value': 33831, 'size': 4}
2017-01-26 18:23:49: ztree:get 0:4/basic => {'value': 100}
2017-01-26 18:23:51: ztree:get 0:2/configuration/37 => {'value': 13871106}
2017-01-26 18:23:59: ztree:report 0:6/sensor_multilevel/power => {'value': 1.3}
2017-01-26 18:24:01: ztree:get 0:10/meter => {'previous_value': None}
2017-01-26 18:24:02: ztree:get 0:4/meter => {'previous_value': 33846}