I think this might be just part of the design and not technically a bug, but I find it exceedingly frustrating and I would be shocked if others didn’t feel the same way.
The design has basically 3 columns the Index (left), the documentation (middle) and examples(right). If you expand a section in the index such as “Site Settings Security” and then scroll down (or up) the index past the bottom the documentation column begins to scroll. When the documentation begins to scroll and a topic moves to the top the index jumps back to highlight the new topic, moving the whole index section back to where you were. This makes navigation feel like an endless loop where you don’t seem to get any closer to where you are going. If possible the middle section should not scroll when the index reaches the end, or the jump to the topic in the index shouldn’t happen unless the mouse is currently in the documentation section.
I can do a screen capture video of this happening if it isn’t clear.