Randon Failure to Execute Alexa Sunrise Routine

I have a smart plug connected to a lamp, and on Alexa, I have it set up to turn on at sunset and turn off at sunrise.
It will ALWAYS turn on at sunset, but will occasionally not turn off at sunrise.
This morning, it happened again.
According the Alexa, the sunrise routine was triggered, but on the SmartThings side, there was not history of the plug going off. It did immediately (and always does) respond to a voice command.
I have yet to figure out if there’s any pattern.
ASIDE from the fact I could probably do this all on the SmartThings side, does anyone have a clue as to why and/or where this command chain is failing?

More info needed:

Brand/model of the smart plug?
Just to clarify - you are using Alexa Routines?

The plug is a Honeywell ZW4103 (Z-Wave).
I am using using Alexa routines for sunrise/sunset.

This morning on the Alexa-side, the routine history says is was triggered.
However, on the SmartThings-side, no command was sent to the plug.
I do not know if there is any way to see the Alexa->SmartThings communication.
Did Alexa not send the command, or did SmartThings not receive/accept/respond to the Alexa command?
Or is it something else?