That’s a great question! I’m Daniel, I assist Katherine by answering questions here at Voicebrew.
I am not sure why your routine doesn’t always work properly. I would suggest making sure that all your devices (both Echo units and smart plugs) are connected to your 2.4 GHz WiFI network for the best results.
Once you’ve confirmed that, if the issue is still happening, I would reach out to the smart plug manufacturer and see if there are some troubleshooting steps they would recommend.
Please reach back out with what the manufacturer says!