So, I see you've solved it but I actually had this problem at one point and your solution isn't how I solved it. It could be a "tomato, tahmato" thing but this info may help?
for every X instance > system > create object ___ > at [random (Z, Z), random (Z, Z)
So if the trigger is pressing the space bar then, depending on your layout size and where you want the spawn, the system will create the item randomly between the two X coordinates, and between the two Y coordinates listed -- every time the space bar is pressed.
You can also do a random trigger for the spawn: system > every random (1, 20) seconds > spawn bullet, etc.
Sorry if this doesn't help at all -- not sorry if it does.