Why It has a space between Fragments of Header and Row ?

[Slim1991]

It's a space with gray background color of your own picture in your blog.
https://cdn-images-1.medium.com/max/800/1*oIFbcdjYrIqxU55-B23tjA.gif

[dextorer]

This was just a POC. For the reference implementation, please take a look at Sofa.