Filter by BoolMask

Hi everyone,
I am having this problem with boolean musk.
I fed the List.FilterbyBoolMusk node with a list of rooms and filter it with a musk coming from DoesIntersect node.
The node works but the result is not correct. As you can see the DoesIntersect node has at least 1 true value in each list but the List.FilterbyBoolMusk gave back 3 empty lists.
Can anybody tell me why?

List.Flatten after BoolMask and connect to element.