Efficiently managing route invalidation is important in Wireless Sensor and Actuator Networks (WSANs), mainly when downward traffic, from root to actuator nodes, commonly occurs. The No-Path Destination Advertisement Object (NPDAO) mechanism for route invalidation was initially proposed in RFC 6550. This approach can sometimes be inefficient, leading to stale routes, high overhead, and lower packet delivery ratios. A newer method, introduced in 2021 by RFC 9009, uses the mechanism through Destination Cleanup Object (DCO) messages for route invalidation. This paper implements DCO in Contiki-NG and compares its performance to NPDAO using the Cooja simulator. In the evaluated scenarios, the root and nodes within the tree send packets downwards to nodes that switch parent. The two route invalidation mechanisms are compared in scenarios with and without probing of the parents. The results show that in the most favourable scenario, the mechanism in RFC 9009 improves packet delivery ratio (PDR) for downward traffic from 66\% (NPDAO) to 97\% (DCO). Moreover, probing significantly improves network recovery times, which contributes to reliability. These findings validate and extend RFC 9009{\textquoteright}s claims, confirming DCO{\textquoteright}s suitability for WSANs.