Illegal_state_exception with reason unexpected byte [0xff]

[iam.Carrot (Aditya Sharma)]

Hi I am using elasticsearch to search through data. I get the below response:

{
   "error": {
       "root_cause": [
          {
           "type": "illegal_state_exception",
           "reason": "unexpected byte [0xff]"
          }
       ],
       "type": "search_phase_execution_exception",
       "reason": "all shards failed",
       "phase": "query",
       "grouped": true,
       "failed_shards": [
          {
             "shard": 0,
             "index": "locationdb_160",
             "node": "31mUy4upTjqVgE6mPZo9Zg",
             "reason": 
             {
                 "type": "illegal_state_exception",
                 "reason": "unexpected byte [0xff]"
             }
          }
       ]
     },
     "status": 500
}

below is my query:

{
"query": {
"bool": {
  "must": [
    {
      "query_string": {
        "query": "location",
        "fields": [
          "pop_nme^1.0",
          "c_keywords^1.0",
          "poi_nme^1.0",
          "poplr_nme^1.0",
          "sb_nme^1.0"
        ],
        "use_dis_max": false,
        "tie_breaker": 0,
        "default_operator": "and",
        "auto_generate_phrase_queries": false,
        "max_determinized_states": 10000,
        "enable_position_increments": true,
        "fuzziness": "0",
        "fuzzy_prefix_length": 0,
        "fuzzy_max_expansions": 50,
        "phrase_slop": 0,
        "analyze_wildcard": true,
        "escape": false,
        "split_on_whitespace": true,
        "boost": 1
      }
    }
  ],
  "filter": [
    {
      "geo_distance": {
        "dist_loc": [
          77.217423,
          28.63146
        ],
        "distance": 10000,
        "distance_type": "arc",
        "validation_method": "STRICT",
        "ignore_unmapped": false,
        "boost": 1
      }
    }
  ],
  "disable_coord": false,
  "adjust_pure_negative": true,
  "boost": 1
}
}
}

What I am I doing wrong?

I had recently migrated to elasticsearch 6.1.3 it used to work quite well on elasticsearch 5.6

I've narrowed it down to the filter section, when I use a geo_bounding_box filter it works just fine: for example:

when I swap the filter with the below code it just works.

"filter": [
    {
      "geo_bounding_box": {
        "dist_loc": {
          "top_left": [
            77.21002578735352,
            28.506712182731704
          ],
          "bottom_right": [
            76.93536758422852,
            28.44937385955666
          ]
        },
        "validation_method": "STRICT",
        "type": "MEMORY",
        "ignore_unmapped": false,
        "boost": 1
      }
    }
  ]