Brother Paper level indicator?

Hi

I bought a brother printer 6400 and played with the paper level indicator…now it doesn’t work as it intends to be. Anyone knows how to fix this?! I asked brother support via online chat, and it sounds like he doesn’t know as well, requesting a callback.

Interestingly I can’t find any related info online…guess it doesn’t interfere the functions, so people just leave it? Anyway any suggestion is much appreciated.

The white thing on the front of the drawer, in the lower right corner? In my experience, it’s quirky. I never trust it.