Mirador viewer

SyntaxError: Unexpected token 'E', "Error from"... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token 'E', \"Error from\"... is not valid JSON",
    "id": "https://iiif.participatory-archives.ch/SGV_12P_01010/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a39b7d1b-b208-4c01-b170-489fa2b9b292",
      "cw-a2a5b503-3cdb-45a4-bb3f-d2fb582b4911"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-54bbf75d-3867-4862-90db-f34e77082cf4",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_01010/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a2a5b503-3cdb-45a4-bb3f-d2fb582b4911",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_01010/manifest.json"
  }
}