When I was placing snow on top of snow (in one-single-layer-of-snow biome) to stack them, they seem to be normal at first.

But just after I added the last layer of snow so that they become a single snow block, the bock that I just created disappeared immediately and only the layer that was generated by the game remained. I repeated the process and the same happened (not just on the same block, but on many other blocks around it, and I am in taiga biome so it couldn't have melted.).

just to give you the seed and the coordinates I did this:
seed: -3136499337269787360
coordinates: -309 63 209