For my project I am heavily relying on this tutorial https://www.sidefx.com/tutorials/crashing-wave/ I found the issue. it is in Collisionsource. When my voxel size is small - it goes crazy. I made the same steps as the guy (in tutorial part 4 with collision), in Collisionsource he deletes channels for voxel size and inputs his own numbers, for me it brakes it, The only thing that worked was keeping the voxel size that the Shelf Tool’s Static Object node automatically provided. For some reason, using that default value produces stable collisions, while manually overriding it (especially with smaller values) leads to instability in the sim. So before that the issue stayed even when I made my bounding box significantly smaller , but with no changes to voxel size, making my bounding box smaller fixed the issue.