wp_editor not working as expected

I have created created a textarea with wp_editor and i want to update the content using wp_post_update.

The problem is that when i try and update the content it removes everything that is already there.

I have tested it with a normal textarea and it works as expected.

The other thing, if i call post_id and insert it into the content it updates.

I hope someone can shed some light on why this is happening.