Board Thread:Support Requests - Getting Technical/@comment-3581054-20161110113608/@comment-24473195-20161111113616

I'd say those galleries are rather weird. There are several wikis that in which each image has a different width and height, example :

http://fallout.wikia.com/wiki/Nick_Valentine

It seems to be because most (if not all) images have the same width and height in your wiki. They do however fit neatly, each image has a uniform width and height and padding. I'd say that the wiki is an edge case, most users aren't disciplined enough to create galleries in such a neat manner. Like noted previously, the caption is the biggest problem. Maybe they changed the maximum width of the text. Impossible to know without checking the previous CSS settings.

There are either css or js hacks that can do what you want, but I suggest  asking staff first.