Post reordering is acting VERY wOnKy

I added the following code to my functions file to add “order” to my stock posts.

add_action( 'init', function() {
	add_post_type_support( 'post', 'page-attributes' );
} );

Reordering looks correct except every post I move looks as if it’s under a parent with “–” or “—” before the post title. If I click “Sort by Order” to refresh, everything kind of jumbles around into a different order than I put them in. They’re more or less in the right vacinity but definitely not where they should be.

Upon further examination, I can see that posts are getting assigned the same order value and it’s grouping those posts together and then sorting alphabetically I think. I tried reordering literally every post and still they’re being assigned the same order value.

How can I fix this?