This sounds like one cause but it appears to me there might be more causes to similar behavior. I just realized that two out of my three sprinklers won’t turn on despite the automation being triggered. A simple restart of the home assistant solves it, all three sprinklers turn on and I do not have any remnants in the automation yaml. So still in the dark rabbit hole.
And what I found interesting is that the automation showed blue box signalling it was triggered but the “last triggered” attribute remained untouched. But, it could be related a bit to the one above described by @frozenmatt because the “last triggered” attribute was about 30mins ago, so I was successful to run the automation recently but I did touch the (turned on/off) device directly in the devices list, which could somehow intervene into the flow of the automation to make at least the timer stuck. So it still could be related to the logic of automation we simply do not observe properly (or which has remnants as in the previous case).