Blog layout becomes corrupted when the page is assigned as the Post page

When I assign my Post page, the page itself becomes corrupted, for lack of a better word. Most of the page is covered in a white tint and the header is duplicated at the top of each blog post. I have tried this with a few themes (my preferred theme being Astra) and I can’t figure out what is happening. The posts are displayed, but since their text color is white you need to select all items on the page to see that they exist.

The moment I unassign the page as Post, the layout returns to normal. This is the first time I have used WordPress or a blog and I can’t figure out if this is due to a setting I have forgotten to adjust. I have been building the page with Elementor, but have also done tests without Elementor and the same corruption exists in a blank page assigned as the Post page.

Can anyone offer some advice on how to possibly correct this?

The page I need help with: [log in to see the link]