XMind Pro 8: boundary + sort creates unexpected result

Hello all,

I'm trying out XMind 8 (XMind 8 Update 8 (R3.7.8.201807240049)) at the moment and I'm puzzled by the result of a sort operation on a node that has boundaries around its children.

For example: 'parent' has 'b-child', 'a-child' and 'c-child' as children. I create a boundary around 'a-child' and add text in it: 'a-boundary'. I do the same for the 'c-child'. I then sort by 'Title' by clicking on the parent and selecting sort -> By Title. The result is that the nodes are sorted but the boundaries are remaining at the same index as before: 'a-child' , 'b-child'+'a-boundary', 'c-child'+'c-boundary'.

I'd expect that the boundaries remain around the nodes that they were drawn originally?