Short answer: Commands are not cached when a device is unreachable.
Long answer: Having intermittently unreachable nodes is a bad thing. When message delivery fails, the Z-Wave protocol stack will re-transmit the message multiple times over different routes. However, the re-transmission process adds latency and extra traffic. The expert UI (
http://IP:8083/expert) provides excellent diagnostic tools for identifying Z-Wave communication problems (Network->Timing Info and Analytics->Packets are particularly helpful). Instead of scheduling the same command multiple times to overcome unreliable message delivery, I definitely recommend you use the Z-Way diagnostic tools to address the underlying problem. Perhaps add a repeater (e.g.,
https://aeotec.com/z-wave-repeater/index.html) or reposition your controller or switch. It's also worth noting the newest Z-Wave.Me controller card (RaZberry 7 Pro) uses an external antenna which provides significantly better RF performance over a PCB trace antenna. If you have a reliable 2.4 GHz Wi-Fi network, an alternative approach is to use a Wi-Fi smart plug that supports Tasmota or ESPEasy (e.g.,
https://www.amazon.de/dp/B0054PSIPA) and control it from Z-Way as an HTTP device.