I just bought the Lionel #394 rotary beacon, and I had the same problem as the rest of you. I adjusted angles for about an hour, then I went on YouTube and looked at the people who had theirs working perfectly, and made my louvers an exact match to how this video had them. It works perfectly now! I used a pair of needle nose pliers to do it.
Shout out to Tomz trainz and accessories if you are on here, Thank You!
Here is the video, and a couple pics of my louvers: https://www.youtube.com/watch?v=ISmNKkcYnwc