Scroll doesn't work with fixed navbar (top and bottom)

I'm submitting a ... [x] bug report [ ] feature request [ ] question about the decisions made in the repository
Do you want to request a feature or report a bug? Bug report
What is the current behavior? When using fixed (bootstrap) navbar - top or bottom - scroll while dragging doesn't work
If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem Try to drag and go down, scroll won't work: https://plnkr.co/edit/KIgEV980cdkUyBy8I7nG?p=preview
What is the expected behavior? Should scroll when hitting the top/bottom
What is the motivation / use case for changing the behavior? Should handle this use case
Please tell us about your environment:
Angular version: 4.4.2
Browser: Chrome 59
Bootstrap: 4 Beta
Other information N/A

akserg / ng2-dnd