bootstrap modal removes scroll bar

This is a feature, class modal-open gets added to the HTML body when you show the modal, and removed when you hide it.

This makes the scrollbar disappear since the bootstrap css says

.modal-open {
    overflow: hidden;
}

You can override this by specifying

.modal-open {
    overflow: scroll;
}

in your own css.

I think that inherit is better than scroll because when you open modal, it will always open with scroll, but when you don't have any scrolls you will get the same problem. So I just do this:

.modal-open {
  overflow: inherit;
}