Using reindex api from kibana fails, but works from curl

[Norman_Khine]

Hello,
A bit of strange issue which I am unclear as to why it could happen, it is related to Merge multiple indices in one

Currently I have a single index where I am reindexing this into a new index using the kibana tools UI, this fails, with mapper [network.latency] cannot be changed from type error and the reindex stops, but if I send a curl command from my terminal like:

curl -XPOST "http://elasticsearch:9200/_reindex?requests_per_second=115&wait_for_completion=true" -H 'Content-Type: application/json' -d'
{
  "source": {
    "index": "analytics-prod-2019.12.30",
    "size": 1000
  },
  "dest": {
    "index": "analytics-prod-2019.12"
  },
  "script": {
    "lang": "painless",   
    "source": "      ctx._source.index = ctx._index;\n      def eventData = ctx._source[\"event.data\"];\n      if (eventData != null) {\n        eventData.remove(\"realmDb.size\");\n        eventData.remove(\"realmDb.format\");\n        eventData.remove(\"realmDb.contents\");\n      }"
  }
}'

the index is fully reindexed!

the only thing I don't have in the curl is "conflicts": "proceed",

what am i missing?

any advice is much appreciated