What happens:
When using a gallery at the beginning of a comment on a talk page, apparently a span data-mw-comment-start with an anchor id is added inside the gallery, which causes the first image to have a larger top-margin. See the examples on dewiki, where it was first reported.
What should happen:
The span should instead be added before the gallery.
This is probably the same issue as T305721, which will be fixed by today's train deployment.
Is there some other issue caused by this span, or just the extra margin? (You're saying they're "broken", which sounds more severe than just a little misalignment, but I don't see any other problems.)
I mean broken in the sense of not working as designed. :) Not sure if a wrongly placed span could cause some more severe issues within a gallery (potentially affecting the rendering of the images themselves). Will keep an eye on whether this gets fixed by the update then!