Воспроизвожу.
Отключил питание, включил. В логе вижу:
Sep 18 07:48:57 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 1 input(s) @ 7 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:57 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 2 input(s) @ 270 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:58 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 10 input(s) @ 5400 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:58 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 3 coil(s) @ 5000 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:59 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 10 coil(s) @ 5100 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:59 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 10 coil(s) @ 5200 of device modbus-tcp:55: Serial protocol error: request timed out
Sep 18 07:48:59 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [serial device] device modbus-tcp:55 is disconnected
Sep 18 07:49:00 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 10 input(s) @ 2 of device modbus-tcp:41: Serial protocol error: request timed out
Sep 18 07:49:01 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: WARNING: [modbus] failed to read 2 input(s) @ 270 of device modbus-tcp:41: Serial protocol error: request timed out
Sep 18 07:49:01 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [serial device] device modbus-tcp:41 is disconnected
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [modbus] Continuous read enabled [slave_id is 41]
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [modbus] Init: Input 1 set input 1 to 1-wire: setup register <modbus-tcp:41:holding: 275> <-- 0 (0x0)
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [modbus] Init: Input 2 set input2 to 1-wire: setup register <modbus-tcp:41:holding: 276> <-- 0 (0x0)
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [serial device] device modbus-tcp:41 is connected
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [modbus] Continuous read enabled [slave_id is 55]
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [modbus] Init: Input 1 set input 1 to 1-wire: setup register <modbus-tcp:55:holding: 275> <-- 0 (0x0)
Sep 18 07:49:12 wirenboard-AWI3MCGC wb-mqtt-serial[28090]: INFO: [serial device] device modbus-tcp:55 is connected
То есть - соответствует ожидаемому.