The PHP post_max_size and/or Nginx client_max_body_size setting should be consistent with the max file size set in the Content Types on binary base field (BinaryFile, Media, Image) other wise the content edit form might not work while the content is valid.

See EZP-25236
I guess, this should be mentioned in this page:
https://doc.ez.no/display/EZP/Requirements+for+doing+a+normal+installation