Sorry if the title is a bit strange, but it's hard to phrase simply. Basically, (on the regular void ray), if you attack using a void ray, no beam appears. If you move, then attack again, there's a beam this time. I haven't the faintest clue why. As far as I know, I didn't make any changes to the void ray, and this has only been happening since the most recent patch. This map uses campaign dependencies, but I thought that I fixed most of the issues with that.
Go into the model section of the data editor, find the Firebat Attack Flame. Under flags you'll find a flag called "Ignorable" check-marked. Simply remove the check-mark and your firebat attack -should- show up 100% of the time. This might have some kind of negative effect but none that I've ever noticed.