Code to ensure next button always leads to next block

I know that when users re-enter a survey with their custom link, it automatically takes them to where they left off. However, even if they use the table of contents to navigate back to the beginning, the next button always redirects them to whichever block it thinks they left off at (thereby skipping several blocks and forcing use of the table of contents to get them where they want to go).
How do I ensure that the next button always leads to the very next block (and the back button always leads to the previous block), regardless of how much of the survey users have completed or whether they are re-using their custom link prior to submission? I tried using branch logic and it just isn't working the way I need it to, so I'm hoping JavaScript is the way to go here.
(I don't really know JavaScript, but I can copy/paste code, figure out its function, and alter it to get it to do what I want as long as I have a place to start.)