How do I spawn sprites which don't overlap each other and are randomly placed in a grid?

I have a grid and want to spawn sprites randomly and are not overlapping each other. But once in a while, one, two or even three sprites overlap even though I destroy the sprite they are spawning on. Any advise?

Trigger Once

pick a random instance of SP1 &

SP2Family is not overlapping on SP1 : spawn SP2(turn left) on SP1

: destroy SP1

Repeat 2 times

pick a random instance of SP1 &

SP2Family is not overlapping on SP1 :spawn SP2(circle) on SP1

: destroy SP1