Lightbox not working anymore - W3 Total Cache

I hope someone can help me with this.

When I want to open an image the lightbox isn’t working anymore, it just keeps loading. I already tried disabling all plugins except for the required ones and I noticed that the Plugin “W3 Total Cache” is in some way causing this problem.

When I disable W3 Total Cache the lightbox is showing up again, BUT the username and the comment field aren’t visible.

I don’t know why it’s suddenly not working anymore, because it did work before - even with the W3 Total Cache plugin.