How to see which prefab produces the error?

To find out what called the despawn, look at the stack trace with that error (line numbers). The C# class at the bottom of that is its origin.

The active count is the yellow button for the Pool Item that says something "10/50", where 10 is the number of items spawned. So click that button and all 10 will be selected in the Scene. Then go click on each one and see if it produces a Console error.