Occasionaly a sub-grouping header gets missed
I've tried to find some sort of pattern to the behaviour, to make a more useful bug post, but I can't find any rhyme or reason to it.
The only thing, if I change the grouping tag to another grouping, save the tag and refresh the page, the new sub-grouping shows.
If change the grouping back to the correct grouping, save and refresh, the tag is missing again. And that's not confined to any single grouping tag.
The only consistent thing is that when it occurs, it's always the first grouping sub-header after the grouping header.
Maybe it's some sort of spacing issue for the panel?