Thank you for sharing the scene. Unfortunately, I am not a LW user.
Is your caustics blur set to 0? I did forget to mention that one.
I remember having a scene-test laying around, with diamond assets. I remember that I abruptly stopped the on-going rendering calculation being the reason why there is still some visible "noise" (lack of samples). Yet, the shadows are sharp as well as both reflective*/refractive caustics
*In the surrounding area, around the diamonds.
An other scene where an HDRI is used as a light source, the caustics pattern comes from the HDRI's lights of an interior.
I am sure that there are even better examples out here online. In fact, here are some of them:
• By PlasmaPeppers#5799 from the Octane Discord server: https://cdn.discordapp.com/attachments/ ... nknown.png
• By Mehrbod#2775 from the Octane Discord server: https://cdn.discordapp.com/attachments/ ... wn-694.png
and certainly more out here.
PS: I do not know the scene-scale verification was made. If the scene-scale is correct, a small plain hard and strong light should not produce soft shadows, generally speaking for both rendering and in reality.