Semi-transparent Geoshell casting shadows, bug or physical consequence?

Hello. I applied a geoshell to a Genesis 8.1 model and tried to do two things:

1. apply a shader called “iray uber water thin”

2. apply a shader called “iray uber water”

The first one worked correctly, but the second one blocks the light, creating a shadow effect that looks like a glitch. Here is an example with an image:

https://drive.google.com/file/d/1OII186VAbod3qxq72H4GsJRD-fYb4Iug/view?usp=sharing

Okay, maybe it's just a normal physical effect, right? After all, the water shader must have been made with larger bodies of water in mind.

However, I've seen this same pattern of interference between shaders and shadows happen with products designed just to make skin look slightly wet. I've tried:

1. Modifying the “offset distance” of the geoshell

2. Placing the model at coordinates 0,0,0

3. Changing all rendering optimizations (memory, caustic samples, etc.)

But nothing worked. Only by slightly reducing the geoshell's “cutout opacity” can I get rid of the shadows, but I don't think this is a real solution...

Does anyone have a better idea of what is happening?

EDIT:

I ended up noticing that the "thin walled" On/Off option is the difference between the two shaders. The “thin walled” option considers the shader to be just a film and there is no shadow projection. But I wanted the shader to be understood as if it were volumetric water, without the thin walled opton, and still without blocking the light. If anyone knows how to solve this, I would be grateful...