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_00788/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-55394180-195d-4e59-b31b-5c6062b3a09b",
      "cw-74c71bfd-1519-4889-b870-ab5a030f5c04"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-6f42a752-fad4-4134-b072-ece7777a218d",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00788/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-74c71bfd-1519-4889-b870-ab5a030f5c04",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00788/manifest.json"
  }
}