Stems don't obbey!

Why Stems are so rebel? Am I doing something wrong?
I am writing for harp in an orchestral piece, and I was expecting to use the stem direction tool to put some groups of notes up and some down, which is usually how you tell left from right hand easily. (Another way would be to put left and right hands in different staves, which isn't very nice with Notion because it doesn't have the cross-staff thing).
The problem is, I can't have stems my way. They only obbey me if they are not beamed together, even if every note in the beamed group has the same direction.
See this example, it's the same measure but I 'cutted out' all the beams. In the first measure, stems are not beamed but they point the right direction. In the second measure, once beamed, they do as they want.
Here's the notion file:
I am writing for harp in an orchestral piece, and I was expecting to use the stem direction tool to put some groups of notes up and some down, which is usually how you tell left from right hand easily. (Another way would be to put left and right hands in different staves, which isn't very nice with Notion because it doesn't have the cross-staff thing).
The problem is, I can't have stems my way. They only obbey me if they are not beamed together, even if every note in the beamed group has the same direction.
See this example, it's the same measure but I 'cutted out' all the beams. In the first measure, stems are not beamed but they point the right direction. In the second measure, once beamed, they do as they want.
Here's the notion file: