Collapsible list gives extra width when expanded?

Collapsible list gives extra width when expanded?

Hey,

I have a collapsible list on my mobile site. The problem is that when i expand the list, it comes with some sort of width which makes the page larger than the screen, which shouldn't happen. This makes that i can scroll horizontally..

Does anyone have a clue what could cause this problem?

Sincerely

Niek