My burger icon changes into a back button

My burger icon changes into a back button when I go to the menu and back to a section ( in my case the first section).

When I’m in my section and click on the burger icon (at the top right corner), the menu opens. I click on another section. That section opens and the menu closes. So far so good.

Now I click on the burger icon again. The menu opens. I select my original section. This is when it gets weird: the menu closes. And the burger icon on the top left corner changes into a back button. And my selected section swipes in from right to left.

I can’t remember I ever implement it like that.

Has anyone ever got the same issue or knows where I can change it back?

Can you post a CodePen?

E.g.:

Currently not. But the only change I made was with “promises”. It kind of changes how the menu bar works.