The second and third box are given box-flex:1. The first and fourth are given widths. The third box, with more content than the rest is hogging more space causing the second box to collapse down to one word per line with the words protruding.
1 - Lorem Ipsum only a little bit now. Lorem Ipsum only a little bit now. But add even a slight difference...
2 - Lorem Ipsum only a little bit now. Lorem Ipsum only a little bit now.
3 - Lorem Ipsum only a little bit now. Lorem Ipsum only a little bit now. Vary the content be even a tiny bit, and the box with more content (or the first one) will grow larger than the rest.
4 - Lorem Ipsum only a little bit now. Lorem Ipsum only a little bit now.