its a combination of all 3, there are no errors in the workflow but i noticed that if you navigate at a moderate pace this does not happen.
Heres the link you can try it out for yourself https://constructco.in/version-test?debug_mode=true
Try spamming one of the categories and the back button and try it slowly. You will see what im talking about. In this case I know that the main page is overlapping because of the search but i dont understand how as its supposed to be hidden and i have even set it to collapse when hidden.