Blueprint Runtime Error: "Accessed None trying to read property"

Are these reference objects persistent or are they spawned themselves?

Do you have more than one level? (ie. Sublevels?)

Did you create this project from scratch or is it something prebuilt that you’re building on?

The reference objects are just simple meshes that give the spawner a translation to work with, correct? Then are you absolutely certain they aren’t destroyed or despawned at any point in time?