Quick answer: Unreal Niagara render target accumulating data between emitter ticks? Shared target across emitters; clear required between - explicit clear pass.
Heat map post-process: emitter A writes; emitter B writes; emitter A's writes shown twice.
Add clear pass
Per-frame initial pass clears the RT. Emitters write fresh data.
Or use separate RTs
Per-emitter RT; combine at the end. More memory; cleaner ownership.
Set RT clear color in setup
RT inspector > Clear Color. Per-frame clear at write-begin time.
“Shared resources accumulate. Explicit reset is the discipline.”
Audit RT usage in your VFX pipeline. Shared RTs without clears are the common bug source.