I noticed that if I have an actor firing bullets with a wait, if I repeatedly press start the bullets are fired continuously without pause. I cannot solve this in any way. I have noticed the same problem in many games made with gb studio.
Another thing you could do is add a loop like this:
Just replace 69 with the number of frames you wish to pass until the next part of the script runs (1 second is around 60 frames; you may need to do this more than once for values above 255).