Quick answer: Unreal Niagara CPU emitter SpawnBurst skipping when CPU budget is low? Per-emitter budget cap; emitters exceeding skip - raise budget or tag as critical.
Boss explosion authored at 1000 particles. Heavy frame; burst spawns 200. Boss looks broken.
Tag as critical
System > Effect Type > Critical Significance. Skips budget caps.
Or raise budget
Niagara budget config; raise on bosses. Per-emitter or per-system override.
Profile under load
Heavy frame test. Budget skipping is visible in the Niagara debugger.
“Niagara budget skipping is a quality optimization. Critical effects need to opt out.”
Mark your hero VFX as critical at authoring. The opt-out is small; the consequence of missing it is visible.