SharePoint list column formatting schema do not resolve

I have the following column formatting:

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
  "elmType": "div",
  "txtContent": "@currentField",
  "attributes": {
    "class": "=if(indexOf(toLowerCase(@currentField),'07') != -1, 'ms-fontColor-redDark','')"
  }
}

The first line give the following error: $ref '/properties/attributes/class' in 'https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json' can not be resolved.(768).

Replacing the schema link to https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json throw the same error.

The list did work properly last week, and with no changes to formatting I get this error and I have no idea on how to troubleshoot this.

Edit: I can open the JSON links in my browser and from what I can tell it looks OK.