it seems to happen mostly when there are two or more summoned bats at once,.
as for how close they are when it happens, they still intersect with the attack animation, so it should count as them being hit by the attack.
I believe I've found and fixed the issue with the projectiles :) I'll update the game asap, once judging for the jam is over. As for the bats, could it be that the attack is only hitting their wings? Their hit box does not include their wings. If not, is there any chance you could send me a quick video showcasing this little bug? That may make this easier to pin down what is going wrong. Thank you for taking the time to tell me! :)