Emitter with zero rate in Cascade unable to be turned on via BP parameter?

I have a particle system containing 3 emitters that have their Spawn rates controlled by parameters in blueprints using “DPM Direct”.

On each emitter in Spawn > Rate I have the “Constant” value set to 0 so that I can turn them on in the blueprint using “Set Float Parameter”.

However setting spawn rate Constant at 0 seems to result in me not ever being able to turn the system on at all.

If I set any of the Spawn rate constants in the particle system in Cascade to a non-zero like “0.5” the TurnOn function works and all the emitters are at the right rates - (expect of course that one emitter being on at the start)

If I run a “TurnOff” function after that to set the rates back to 0 and then run TurnOn i can successfully turn them off and on at will.

So i figured a workaround was to put a non zero spawn rate in Cascade and then run TurnOff at BeginPlay. That does indeed turn the particles off. But TurnOn then has no effect just like before.

So I’m wondering if there is some sort of performance or culling thing that essentially deactivates the system because no emitters are active at runtime? Or maybe there is a another way I should be doing this? Or maybe this is a bug?

The significance of the emitters is “critical” I turned off “can be baked” in case that had something to do with it.
None of those seemed to have any effect.

So in case anyone sees this the solution turned out to be not using Parameters but calling Activate/Deactivate on the Particle Actor in blueprint.