Board Thread:Support Requests - Designing Your Wiki/@comment-5221255-20130727140544/@comment-3030984-20130727142655

The English wiki is using an older script for collapsible tables. Wikis now have this script built in, but you need to change the template slightly.

Replace all instances of 'collapsible' with 'mw-collapsible', and 'collapsed' with 'mw-collapsed' in your template. It should then work fine.