Update restrictions on ElasticSearch Object type field

Question

I have to store documents with a single field contains a single Json object. this object has a variable depth and variable schema. I config a mapping like this:

"mappings": {
    "properties": {
        "@timestamp": {
            "type": "date"
        },
        "message": {
            "type": "object"
        }
    }
}

It works fine and ElasticSearch creates and updates mapping with documents that received. The problem is that after some updates in mapping, it rejects new documents and do not update mapping anymore. At this time I change the indices and mapping update occurred for that indies. I'm looking forward to know the right solution.