Error `400` on

I’m getting error 400 on
Request Method: POST
Status Code: 400

It happens when I:

  • try to install or delete a plugin
  • try to update a post
  • I also noticed that when I’m on the post overview page (, WordPress keeps logging load-scripts.php?c=0&load(chunk_0)=jquery-core,jquery-migrate,utils&ver=5.7.2:2 POST 400
    every 15 seconds to the Google Chrome developer console.

What I tried:

  • added IUSR, NETWORK SERVICE, IIS_IUSERS with full permissions on wp_content folder
  • deactived all my plugins
  • added debug to wp-config.php, but very little and nothing of interest gets logged
  • Set permalinks to Plain
  • plugin Health Check ( reports The REST API did not process the context query parameter correctly.
  • Tried reinstalling WordPress and restore my database

What else can I try?

I checked here: