I face 2 problems in the following Beamer example:
For the section "Table of contents" and "Introduction" circles representing each of the slides do not appear (only for the following ones), even when there are several.
Furthermore the circles do not appear below the title of the section, and hence it can be misleading to know to which section they belong.
I dont know if this is the answer you are looking for but the pages with sections will be created only if you make a frame. Look at the below code.
Keep in mind that sometimes the pdf viewer redirects the section link on the ToC to the bottom (or the top) of the correct page leading you to think that the link is incorrect when you are using the windowed view. In the full screen mode it should work just fine.