When there are many (long) comments, it is not possible to scroll through the comments which are shown below a certain point of the last page. This seems to be due to the fact that scrolling does only work in relation to the pages.

I can scroll when clicking and dragging the scrollbar, but doing this the scrolling does not work properly either. For example, releasing the mouse button does not release the scroll bar, and jumps happen.

I would expect that it is possible to scroll the comments independently from scrolling the page. 

One workaround is to add empty pages to the end of the document, though this is not very convenient.

I have tested this both on our own install and the collabora online demo with firefox. But our team reported the same issue for other browsers.