Quick answer: Unreal PCG graph swapping static meshes via Replace failing on ISM components? ISM stores by per-instance index; replace requires Remove + Add.
PCG should replace one tree variant with another; ISM still shows the old.
Remove and Add
Per-instance Remove, then per-instance Add with new mesh. Effectively replace.
Or use HISM with switching
Hierarchical with mesh switching support. Modern engine; cleaner.
Audit PCG outputs
Each PCG output's intent; verify execution.
“ISM is index-keyed. Replace = delete + add.”
If your PCG replacement doesn't apply, the per-instance lifecycle is the source. Document.