If you have OctaneRender 2022.x or newer version, we don't recommend "Fake Shadows" and you try:
- to change the render kernel to "Photon Tracing" (PHT),
- to check "Allow Caustics" for specular/universal material(s) (eg: glass, water...),
- to reduce "Photon Gathering Radius" for find the ideal focus of caustics at PHT kernel settings.
Happy rendering!