The kernel nodes don't have now the volume step option, this feature is now available in the volume medium node, that is the node that you should use to render the volume objects. I will try to post a sample scene ASAP.
From the release notes:
- Moved the volume step length from the kernel node to the volume medium node. This allows you to tweak the value for each volume and depending how close and how big they are.
Anyway, the Octane API MSG can be a bug in the plugin. Let me check this problem and the other issues you have.
Computer Graphics Software Developer
Octane plugin development and support: LightWave and Houdini