This should be resolved now.
It has to do with the order tags are embedded. Say you're quoting someone who has used a spoiler tag.
Forum Shark wrote:NSFW under the cut[spoiler]Just like this.[/spoiler]
The forum language for that should be
(quote="Forum Shark")NSFW under the cut
(spoiler)Just like this.
(/spoiler)(/quote)If you change the order the tags close, the page will break. For example:
(quote="Forum Shark")NSFW under the cut
(spoiler)Just like this.
(/quote)(/spoiler)Note that the ending (/quote) and (spoiler) have been reversed, and aren't closing the BBC code in the right order.
TL;DR: make sure to close your tags properly!