Industrial Control Systems are often found today in critical infrastructure and utilities such as power generation facilities and water processing plants. Within this automation solution often lies the unassuming controller quietly monitoring and controlling these processes using Input/Output (I/O) devices. Failure within these kinds of systems can often incur high economic costs and in the worst case loss of life. A common method of increasing reliability within controllers is using standby redundancy, whereby a redundant backup controller is ready to take over should the primary controller fail. However, when realising redundancy using open62541, an open source implementation of OPC UA, we find some issues. Because there are no mechanisms implemented in open62541 that automatically handle redundancy, if a failure happens, the backup would not be able to seamlessly continue operations. This study includes an investigation of what internal states must be synchronised between primary and backup, a proposed solution implemented in C, including failure detection and synchronisation functionality, and finally an experiment for validating the artefact. The result shows that using the redundancy module, a seamless failover can happen within a 100 millisecond deadline.