Custom Language Plugin: Folding one range folds all ranges

Sorry, here is my code:

@Override
public FoldingDescriptor @NotNull [] buildFoldRegions(@NotNull PsiElement root, @NotNull Document document, boolean quick) {
    FoldingGroup group = FoldingGroup.newGroup(someName);
    List<FoldingDescriptor> descriptors = new ArrayList<FoldingDescriptor>();
    PsiElement element = getNext2(root.getFirstChild());
    while (element != null) {
        PsiElement start = getNext1(element);
        PsiElement end = getNext2(start);  // might be null = end of file
        if (start != null) {
            TextRange range = getBlockRange(start, end);
            if (range != null)
                descriptors.add(new FoldingDescriptor(start.getNode(), range, group));
        }
        element = end;
    }
    return descriptors.toArray(new FoldingDescriptor[descriptors.size()]);
}

Do they have to be different groups?  The tutorial used only one group, though.

Yes, I do have to use different FoldingGroups ...

from Javadoc

> * {@link com.intellij.openapi.editor.FoldRegion}s with same FoldingGroup instances expand and collapse together.