Quoted from n1teowl:
I have been having the same issue. The drop target won't drop itself, it will only drop if hit. This is especially a problem when playing multi-player games as the target will often remain up when the next player starts. I took a look at the solenoid and the brass actuator that is attached had snapped off. There is a thin piece of metal that activates the drop target when the solenoid engages. I found a replacement on Marco, it's #01-8647-R. I hope that helps.
Thanks for that. The arm wasn't the issue, but the spring holding it was. I loosened it and it works fine. But the as I wrote in a post before, the target stays up sometimes anyway and I'm convinced this is a software bug.