Gallery broken after update to v1.3.0

Hi guys,

we were using "Thumbnail Grid" as a Gallery format for the posts in our blog articles. Everything was great, but I checked the site today again and all the galleries were/are broken.
Here is an example: http://www.pebblestuff.io/tips/how-to-set-up-television-on-pebble-time-when-youre-stuck-in-configuring/

Instead of showing the thumbnails in a grid format, it shows them in a vertical layout just one above the other. Doesn't really look good and we are having a lot of people visiting this article right now.

My assumption is that it is because the update of the template (because it worked earlier today) but I'm not 100% sure.

Can anyone help me here? How can I fix this?
Do you need any other information about our website, plugins or something else?

Thanks a lot and Cheers,

Marko