problem:
valid json responses get tagged by resourceresponsevalidator as non valid

description:
I am a bit of a loss debugging an suddenly emerging error on my local dev environment (MAMP, php 7.4, D8 and D9) where totally valid json responses get tagged as non valid.
The json is partly generated bij Drupal and parts come from an external unrelated source.
Reports gives me reasons like

  • 'The property data is not defined and the definition does not allow additional properties'
  • 'Object value found, but an array is required'
  • 'The property value is not defined and the definition does not allow additional properties'
  • etc.

The only way to avoid this is bij setting assert_options(ASSERT_ACTIVE, FALSE);  in settings.local.php.

(Production - not loading the settings.local.php -  is zooming like a bee, so this is not a pressing issues, it is just that I do not understand the root of the problem.)

question:
Can someone with deeper understanding of the drupal JSON:API shed a light on this for me.