Strange behaviour , indeed ! I personally never had the case. I'm trying to understand what is the plausible cause of your beam being "off".
In the "scene builder" window, the fixtures are on the left hand side and the tools are on the right hand side. OK ?
select your fixture by clicking on it. It should be highlighted with a blue square around it.
Now, in the "Tools" window under the "presets" tab you should have a lightbulb sign. Click it and the fixture selected should turn white or any colour selected in the "Presets" if your fixture is capable of producing colours.
Then you can go into the "position" effect under the "Effects" tab.
Adjust positions and save. Close the "Scene Builder" window
You have now a scene you can visualise step by step under the "Editor" tab and check if the beam is "on" each step (you have also the possibility to adjust each step of your scene by hand). You can visualise the scene in the "Live" tab (under which you can only start or stop the scene, but not edit it).
Check if any fading could keep bulb "off".
I hop this(basic) explanation will help you check what is turning wrong