Custom Blog Page won’t display blog posts

I’m still struggling with the custom blog page I created.

While I was able to figure out that I would have to pick the Advanced Format option in the Theme’s settings to link to the page in the menu, I’ve now noticed that loading the page is often slow and displays only white spaces in the Masonry grid, instead of the image, title and excerpt of the blog post.

I doesn’t happen all the time, but it happens frequently and even refreshing the page won’t help to display the blog posts in the masonry grid properly.

Any ideas or pointers would be greatly appreciated.

Thanks.