Light is in state on, but physically it's not

I have a problem with two of my IKEA Stoftmoln lights. They are connected via ZHA and running fine if triggered from the UI or the cloud.
However, when I’m using them in the blueprint automation “sensor light”, they are sometimes on, sometimes not. Even more confusing, they’re shown as ON, however physically they’re not. Only toggling them to OFF and then ON again via the UI makes them light up again.
One thing in the light history is confusing as well. After triggering them via the UI, a second log entry without any sender is logged. This is when they become unresponsive via the automation.
The lights are located directly next door to the Zigbee stick, the stick is far away from the server, and as already mentioned the light is working fine via the UI.