Here Hubitat developer said:
HSM sends the "siren" command unless you select both strobe and siren, in which case it sends "on" command. That should be changed so that if both selected, it sends "siren" and "strobe" commands, not "on".
I don't remember what driver is doing for "On" but probably that's the issue and probably it has never been fixed on HSM side. I'm using just siren BTW.
