collapsible menu not closing

works on https://www3-dev.tuhh.de/e-10/pontifex/docs/level1/

but not on the nodes, see, e.g.

https://www3-dev.tuhh.de/e-10/pontifex/docs/chapter0/000/

Not sure if it has ever worked...

Same goes for the drop-down menu entry "Information"