Bootstrap dropdown menu not scrollable inside ember-perfectscroll

I'm showing a few lists of items under different categories in kanban view. In each item-list, I use ember-perfectscroll to scroll through the items vertically. And in each item-card, I have bs-dropdown to select from a list of sub-categories. Everything works fine until the item-list grows bigger and needs to be scrolled.

When I want to open and scroll inside sub-categories dropdown menu, the item-list is getting scrolled instead. I'm able to scroll sub-categories menu only for the items which are at the end of the item-list.

How can I make the dropdown menu scrollable by suppressing perfect-scroll ?