It's a type mismatching. I'm facing with such issue too. It looks like you try to index a value into an object mapped json. i.e., you indexed one time something like this:
{
"obj1": {
"field1": "value1"
}
}
and then index this:
{
"obj1": "value"
}
Check your existing mapping via elasticsearch:9200/twitter/_mapping
and you will see if that one of the field was indexed as object