I just implemented a custom culling for our particle systems (as suggested here: https://blogs.unity3d.com/2016/12/20/unitytips-particlesystem-performance-culling/). Our artist then attached the custom culling component to our particle systems.
Everything would be perfect, but then he tweaked some of these particle systems in the future so that they were suddenly capable of the automatic culling. But he forgot to remove the custom culling components, so every single one of these particle systems is being culled twice now (both automatic culled and custom culled).
Possible solution would be to add something like a 'IsAutomaticCullingEnabled' property to the UnityEngine.ParticleSystem class. I could then validate whether the custom culling should be used or not. Or even whether someone forgot to add the custom culling component etc.