I copied the successful curve into the scene with two curves, added an Octane Object tag to the spline curve, and dragged the hair mat onto it as well. It renders as I would expect. You might want to give that a try.

I just tried this in R21.207 and I am seeing two sets of splines animate as they draw on during the shot. I am using a Windows machine. I made sure to set as hair on import, but instead it is coming in as a spline only. That would seem to indicate a bug with Cinema.

Luminous, can you post your scene file, please?

Can you guys briefly describe the steps you are taking?

Can you create a scene in v4 that you can post, with nothing proprietary, that crashes 2020? That would really help to nail down the issue. Or is this problem limited to a specific scene only?

Always a good idea to share your solution. Doing so helps the community.

Perhaps try a Cinema 4D volume object to model the condensation instead? That could get your geo closer to reality and allow Octane to do its thing. It looks like a caustic effect to me. If you change the lighting direction what do you see? Also, have you tried your setup with a simple plane instead ...

Have you tried with a new scene? I see the expected results in R21 and the current Octane 2020 build.

You may want to increase your specular depth. I have found that can work in situations such as this.

Can you post a screen shot of your model mesh wireframe? Quickshade with lines would be great!