Brioche bread won't seal properly. Need help

Hi everyone, I was making a dinner roll from Joshua Weissman's Youtube video. When I shap the dough into ball, I cannot seem to get the dough to seal itself at the bottom. The ball kept opening up and like it doesn't want to blend into a homogeneous ball.

So, I baked them and the crumb separate from each other into different lump as shown in the picture.

I've try the recipe 2 times now, the second time I oil the surface during the first prove (prevent the skin forming). Still no improvement.

Please help, thank you