Shouldn’t UParticleSystemComponent::GetAnyVectorParameter have a conditional for the PSPT_Actor parameter type?
I was tinkering with some beam particle system stuff being driven by instance parameters such as beamStart, beamEnd, and while the beam itself shows up with the correct start and end locations, there are other emitters that have Initial Location set to beamEnd, and they appear to go through the code path that ends up calling GetAnyVectorParameter, but since beamEnd is an PSPT_Actor, it is not found here, and the initial position defaults incorrectly to the Constant value in UDistributionVectorParameterBase::GetValue.
This seems like an obvious oversight in the handling of the parameter types in GetAnyVectorParameter, and it appears to still be this way in github