It means your power went above 100, triggering the automation.
Then it went below 100, but not below 1. So the wait for trigger did not occur.
Then while still waiting in the wait for trigger the power went above 100 again. This re-triggered your automation.
Your automation does not have a mode specified, so it would be using the default mode of “single” which only allows a single instance of the automation to run at any one time. What should happen is that the automation should reject the second trigger, log a warning, and continue waiting in the wait for template. However I believe there there is a bug that actually stops the automation when this occurs. This is not the first time I have seen this sort of thing reported.
You can report this as a new issue here:
Include your automation config and the downloaded automation trace.
Another way to approach this would be to use a template binary sensor to trigger your automation. This sensor should not turn off until the power goes below 1.
Honestly, I had mistakenly understood that I could wait for the first trigger above 100W to start, and then ignore it and wait for the next event when the trigger remains below 1W for 10 consecutive minutes. It’s possible?
However, if I inserted the template / binary sensor, to have it available, would I have to do a complete reboot or would the quick one be enough?
Thank you very much anyway for the sensor already supplied, ready and working