So [this line](https://github.com/plone/plone.restapi/blob/9.1.1/src/plone/restapi/deserializer/__init__.py#L8) is bad: data = json.loads(request.get("BODY") or "{}") With Zope 5.8.4+ this fails when the request BODY is larger than 1MB. See discussion in https://github.com/plone/Products.CMFPlone/issues/3848 and https://github.com/zopefoundation/Zope/pull/1142. See [my summary](https://github.com/plone/Products.CMFPlone/issues/3848#issuecomment-1790665336) of the history and the steps taken so far. Temporarily fixed in https://github.com/plone/plone.restapi/pull/1729 by disabling a Zope form memory limit check.