Filebeat 7.17, error "cannot access method/field [size] from a null def reference" while trying to download IOCs from MISP

Elastic Stack Beats
1

Hello Everyone,
I'm trying to enable MISP integration, using the threatintel module.
Seems that the agent s not able to download the IOCs and I can see only one document in Elastic, with this error message:

cannot access method/field [size] from a null def reference

I cannot see any error message (related to MISP or Threatintel module) in the log files.

This is my config:

misp:
    enabled: true
    var.input: httpjson
    var.url: https://MY_MISP_INSTANCE/events/restSearch
    var.api_token: MY_TOKEN
    var.ssl.verification_mode: none
    var.first_interval: 100h
    var.interval: 5m

Thanks for your support.