Hi Brambil,
You may not be aware of this topic JSON Output Bug? - #3 by abarrow which includes a link to a newer executable only version of Sailwave which fixed an issue with the Sailwave ‘Save as JSON file’. I
You might like to update your version of Sailwave to this newer version. FYI - the latest that is available as executable only is v2-29-6. The JSON file produced by the newer version of Sailwave may be compatible with TablePress JSON importer.
Kind regards,
Huw