Collision bug or am i doing something stupid?

I'm getting a fatal crash from a seemingly simple collision event. It happened both on construct v. 0.99.92 and 0.99.94

The app crashes, seemingly at random, when a cannonball sprite hits and destroys the wall tiles. If you download and try this, you may have to restart the app a few times if nothing happens.

please help!

Here are two different ways to avoid the crash.

First way:

Change event 1 from "Always" to "Start of layout".

On event 2 change the order of actions so that destroy is after spawn.

Disable/Remove event 3.

Second way:

Add "Sprite6" to the family "Red".

Change event 4 to the following:

+ System: For each Sprite6
+ Sprite6: [negated] Sprite6: overlaps Red : offset (0,-2)
+ Sprite6: [negated] Sprite6: overlaps Sprite2 : offset (0,-2)
-> Sprite6: Destroy
[/code:1sii29ky]

thanks a lot! i used the second way and it worked .. i think i understand what i missed.