Well, I was struggling with this myself, even stumbled across this post when researching. I’ve finally found the answer, so it feels only natural to come here and try to help. I’ve already submitted a bug case as well.
Basically, this happens because of the Crowd Visualization trait. Specifically, when the Meshes array within “Static Mesh Instance Desc” has 0 elements, but Params → LODRepresentation is configured to use “Static Mesh Instance” for any one of the entries (High, Medium, Low, Off), it will lead to a crash.
Initializing the Meshes array with any item (even default) will prevent crashing. Similarly, changing LODRepresentation to no longer use “Static Mesh Instance” also prevents crashing. Tested both solutions on 5.4.1.
UE5.3 handled this gracefully by not spawning anything when the configuration was wrong.
Cheers!