Editing terrain by uploading raw file is buggy

I found what I assume is a bug of terrain editing by uploading a RAW file: randomly, even if a piece of land in RAW file is flat, a single peak appear, usually 1mt tall, and similar to a piramyd. Usually in a 256x256 island, six or seven peaks appear in various positions... Getting through with them by terrain editing tool is quite hard since they are smaller than the minimum size of "caterpillar"...