As title suggest, the UParticleSystem properties bIsImmortal and bWillBecomeZombie can be set to true when emitter fulfills certain conditions but are never set to false again if those conditions have been fixed. This leads to SpawnEmitterAttached and …AtLocation dumping screen and log messages that may be false positive.
Only workaround i have found so far is to duplicate the affected ParticleSystem and delete the original, rerouting any references to the duplicated one. This fixes the issue since duplication constructs a new UParticleSystem and bIsImmortal and bWillBecomeZombie are constructed by default as false.