I know multiple devs that have been suffering from this issue since Indoor Dynamic Environment Maps Beta was released… over one year ago. The only hacky fix for this is turning EnvironmentalSpecularScale’s value to 0. This limits the entire Place’s potential for reflections, especially when using PBR materials. Whether its the reflection probe that needs to be changed, or official support of emissive textures, we need this to be looked at soon.
Beams and ParticleEmitters have had LightEmission, LightInfluence properties for years and Beams have a Brightness property. These are desperately needed for Decals and Textures so we can do emissive textures properly, without causing unexpected behavior.