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_10P_00015/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-3eefda35-c39a-4f7b-b720-d249e2eb32e2",
      "cw-a101e306-aedc-4a8e-b70f-f1608b1452f9"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-4c711bac-0dc0-4f41-ac11-f5e47be5c3f6",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00015/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a101e306-aedc-4a8e-b70f-f1608b1452f9",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00015/manifest.json"
  }
}