I have the same exact issue. Zwave network stopped working after multiple restarts of zwave. Here is my OZW log:
2019-01-28 17:20:24.354 Always, OpenZwave Version 1.4.3322 Starting Up
2019-01-28 17:20:36.698 Info, Setting Up Provided Network Key for Secure Communications
2019-01-28 17:20:36.699 Info, mgr, Added driver for controller /dev/ttyAMA0
2019-01-28 17:20:36.699 Info, Opening controller /dev/ttyAMA0
2019-01-28 17:20:36.699 Info, Trying to open serial port /dev/ttyAMA0 (attempt 1)
2019-01-28 17:20:36.699 Info, Serial port /dev/ttyAMA0 opened (attempt 1)
2019-01-28 17:20:36.700 Detail, contrlr, Queuing (Command) FUNC_ID_ZW_GET_VERSION: 0x01, 0x03, 0x00, 0x15, 0xe9
2019-01-28 17:20:36.700 Detail, contrlr, Queuing (Command) FUNC_ID_ZW_MEMORY_GET_ID: 0x01, 0x03, 0x00, 0x20, 0xdc
2019-01-28 17:20:36.701 Detail, contrlr, Queuing (Command) FUNC_ID_ZW_GET_CONTROLLER_CAPABILITIES: 0x01, 0x03, 0x00, 0x05, 0xf9
2019-01-28 17:20:36.701 Detail, contrlr, Queuing (Command) FUNC_ID_SERIAL_API_GET_CAPABILITIES: 0x01, 0x03, 0x00, 0x07, 0xfb
2019-01-28 17:20:36.701 Detail, contrlr, Queuing (Command) FUNC_ID_ZW_GET_SUC_NODE_ID: 0x01, 0x03, 0x00, 0x56, 0xaa
2019-01-28 17:20:36.701 Detail,
2019-01-28 17:20:36.701 Info, contrlr, Sending (Command) message (Callback ID=0x00, Expected Reply=0x15) - FUNC_ID_ZW_GET_VERSION: 0x01, 0x03, 0x00, 0x15, 0xe9
2019-01-28 17:20:36.701 Detail, contrlr, Notification: DriverFailed