Save the unsaved draft outside the failing editor
Protect unsaved editor work, then inspect the failed WordPress REST request and response before changing security or rewrite settings.
Save the unsaved content in an approved private place before investigating the editor's failed response. Do not repeatedly click Publish while the result is uncertain: a request may have saved even if the browser could not interpret its response. Check the post list or open the current post in a separate session to see whether the most recent revision exists. Keep unpublished text and media out of support tickets.
This guide assumes the public site still loads and the fault occurs during an authenticated editor save. If the whole site returns a 403 or 500 response, use that symptom’s platform guide first. The application owner controls WordPress components; a hosting account does not imply Novasean editor or plugin support.
Record the failing request, not its private payload
In the browser’s developer tools, an authorised site administrator can retry a harmless test draft and identify the failed request under the Network view. WordPress’s REST API reference includes post and page routes. Record only the request path, HTTP status, response content type, redirect destination if shown, time and a short safe description of the response. Do not paste cookies, authorisation headers, nonce values, full request bodies or private post content. A login page returned instead of JSON points to an authentication or redirect path; a 403 or 5xx response points to another branch; an HTML warning before the JSON suggests application or PHP output. These are clues, not automatic diagnoses.
Use Site Health and recent changes to narrow the layer
If available, review the WordPress Site Health result for REST API problems and compare it with the editor request. A general REST finding can help, but the particular authenticated save request is the stronger evidence for this symptom. Ask the application owner whether a plugin, theme, URL or security setting changed just before the failure. Do not disable all plugins or hosting security controls blindly. If the response shows a platform block or server error, give support the safe path, status and timestamp for an account-scoped investigation. If application code emits an unexpected response, the application owner should repair or roll back that component.
For example, a failed /wp-json/ request returning an HTML login page suggests an authentication or redirect path. Confirm the exact failing save request; a different REST endpoint may have another cause.
Confirm a draft can be saved and reopened
After a targeted correction, create a harmless test draft, save it once, reload it and confirm its content persisted. Then retry the real post after comparing the saved revision with the private copy. If the test still fails, preserve the new status and time and return to the responsible owner. Do not call a public page load proof that authenticated editor saves work.
Frequently asked questions
Is invalid JSON itself the root cause? No. It describes the editor receiving a response it could not parse as expected; the request status and safe response type narrow the cause.
Should I switch permalink settings immediately? Only when the evidence points to account-level routing, and with a rollback record. A REST save can fail for several other reasons.
Sources and technical references
Related guides
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