Cannot insert data at random times. [OptionalDataException]

[nopma (what)]

I have 3 data nodes. I use fluentbit to send logs to elastic to only one node.
Random times I see that it's failed to send data to elastic. It takes 1h exactly to resolve the issue.
Its happen one per day. Some logs for random host they cannot insert anything for 1h some others they insert like 1/25 for the normal rate.

I cannot understand what happening.

elastic: elasticsearch-oss 7.9.1
Java: openjdk 14.0.1 2020-04-14
jvm options:
-Xms10g
-Xmx10g
14-:-XX:+UseG1GC
14-:-XX:G1ReservePercent=25
14-:-XX:InitiatingHeapOccupancyPercent=30
Specs:
CPU: 12
RAM: 16G

I see only the error message but i don't know if is relative:

{
  "_index": "index_name_2020.11.16",
  "_type": "_doc",
  "_id": "0c561660-8ef6-5375-00f7-41c7736f919a",
  "status": 500,
  "error": {
    "type": "exception",
    "reason": "java.io.OptionalDataException",
    "caused_by": {
      "type": "i_o_exception",
      "reason": null
    }
  }
}

[warkolm (Mark Walkom)]

What do the Elasticsearch logs show at that time?

[nopma (what)]

nothing just the normal message