The first thing I'd do would be to verify your JSON formatting is correct AND the proper required fields and attributes are populated in the JSON. Probably safe to assume you've already done this but have to say it.
Just because workflow isn't enabled doesn't mean it's not using versioning. If you have basic versioning enabled, even without a specific workflow, it will keep a version record when the user saves. I'd highly recommend checking to see if the new pages have any kind of version history ID in the field. If they do, then it will attempt to find that version and serve that version up.