Artefacts in the rendered objects

[Roland09]

I was trying in Unity 2019.1.7f1 with HDRP 5.7.2. It's working quite well except that from certain camera angles there seems to be assets mirrored which destroy the imported vdb object. Looks e. g. like this:

In my case I use a cloud. It seems as if when the cloud is rendered, it's being segmented into smaller pieces and in each of those pieces the environment (in my case trees) cause the vdb object to become transparent at several locations.

Any idea how to fix this? Thank you very much!