# A complete PLC shutdown due to OPC UA?
**URL:** https://www.wago.community/t/a-complete-plc-shutdown-due-to-opc-ua/2888
**Category:** CODESYS
**Created:** [September 22, 2026, 12:53pm UTC](https://www.wago.community/t/a-complete-plc-shutdown-due-to-opc-ua/2888 "2026-09-22T12:53:57Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@TomasD](https://www.wago.community/u/TomasD)
#### Post date: [September 22, 2026, 12:53pm UTC](https://www.wago.community/t/a-complete-plc-shutdown-due-to-opc-ua/2888/1 "2026-09-22T12:53:57Z")
I’ve run into this problem (not for the first time) where my PLC freezes, and the only thing that helps is a reboot.
I found the following in the logs:
runtime.log.1
Sep 22 09:16:26 localhost codesys3: CmpOPCUAStack DEBUG OpcUa\_TcpListener\_CloseConnection: Error 0x00000000 removing connection 0xb21ef208!
Sep 22 09:16:26 localhost codesys3: CmpOPCUAServer EXCEPTION Unhandled exception in OPC UA server. Please restart the PLC.
Sep 22 09:16:26 localhost codesys3: CmpSupervisor DEBUG Description=Exception occured within the OPC UA Server
Sep 22 09:16:26 localhost codesys3: IoDrvDal DEBUG stops triggering driver-watchdogs; failure info from CmpSupervisor
Sep 22 09:16:26 localhost codesys3: IoDrvDal DEBUG Component ID=0x00000124 is out of order! Vital operation ID=0x00000001 failed!
Sep 22 09:16:26 localhost codesys3: IoDrvDal DEBUG Operation description: ‘Exception occured within the OPC UA Server’
Sep 22 09:38:54 localhost codesys3: IECVisualization DEBUG Visu\_PRG: Creating Client for Extern-ID: 2469809092
Sep 22 09:38:54 localhost codesys3: IECVisualization DEBUG Visu\_PRG: Creating Client successful for Extern-ID: 2469809092 Returned IEC-ID: 1
Sep 22 09:51:19 localhost codesys3: IECVisualization DEBUG VisuFctCheckForUnusedClients: Removing Client with IEC-ID: 1
Time delta: T#45s985ms Locks: Paintbuffer: TRUE
Sep 22 09:51:19 localhost codesys3: IECVisualization DEBUG VisuFctCheckForUnusedClients: Successfully Removed Client at Address: 2999433664, IEC-ID was: 1, EXT-ID: 2469809092
Sep 22 09:53:22 localhost codesys3: IECVisualization DEBUG Visu\_PRG: Creating Client for Extern-ID: 975774383
Sep 22 09:53:22 localhost codesys3: IECVisualization DEBUG Visu\_PRG: Creating Client successful for Extern-ID: 975774383 Returned IEC-ID: 1
Wago Ethernet settings status:
Error code: 9
Argument: 5
Unknown blink code 9 / 5
More details about this blink code, refer to the manual of the device.
Has anyone else run into this problem? What should I do?
Maybe I’m looking in the wrong direction? Where should I look if the problem occurs again?
---
### Author:  [@WagoTorgeir](https://www.wago.community/u/WagoTorgeir)
#### Post date: [September 22, 2026, 1:25pm UTC](https://www.wago.community/t/a-complete-plc-shutdown-due-to-opc-ua/2888/2 "2026-09-22T13:25:57Z")
Hi Tomas,
The described symptom resembles one of the problems which has been solved in FW31; what firmware version does your PLC run ?
---
### Author:  [@TomasD](https://www.wago.community/u/TomasD)
#### Post date: [September 22, 2026, 2:00pm UTC](https://www.wago.community/t/a-complete-plc-shutdown-due-to-opc-ua/2888/3 "2026-09-22T14:00:03Z")
It’s been working for about a week, and now I’m getting an error.
PLC 750-8212
Version 04.09.01(31)