When the volume cloud + Movie Rendern Queue tool is used for high-resolution rendering, the pixel shape image of the cloud appears?

When I use the volume cloud in the scene and prepare to use the new Movie Rendern Queue tool for high-resolution image rendering (using the High-Resolution Rendern module), the volume cloud appears very obvious pixel dots in the rendering, just like the following image:

Even sometimes, there will be tears in the picture:

This is the rendering setup I use when rendering

The engine used is 4.26. This problem only occurs when the High-Resolution module is used. It is normal when the image is output without the help of high-resolution rendering;

I tried to use many methods to improve the quality of volume cloud, but the problem has not been solved. I don’t know whether it is my setting problem or the bug of the engine itself;

No one can solve this problem? I tried a lot of methods, and even tried the latest 4.27. This problem still exists!