Kafka-> S3- invalid header field value for \"X-Amz-Meta-Kafka_key\"

Hello!
I'm afraid the thing I'm reporting is not a bug per se, but I find it exceptionally difficult to figure out the reason for the error.
I'm using pretty standard configuration to consume messages from Kafka (attached below), but I'm getting rather cryptic error

Failed to send message to aws_s3: RequestError: send request failed
caused by: Put \"<HTTP S3 URL>\": net/http: invalid header field value for \"X-Amz-Meta-Kafka_key\"

I'm using jeffail/benthos:4.9.1.

Can it be caused by unprocessable keys for key/value pairs in Kafka?

    input:
      kafka:
        addresses:
          - ${KAFKA_ADDRESSES}
        client_id: ${CLIENT_ID}
        commit_period: 3s
        consumer_group: ${CONSUMER_GROUP}
        group:
          heartbeat_interval: 3s
          rebalance_timeout: 60s
          session_timeout: 10s
        checkpoint_limit: 1
        batching:
          count: 1024
          period: 1s
        max_processing_period: 2s
        start_from_oldest: true
        target_version: 3.2.0
        topics:
          - ${INPUT_TOPIC}

    pipeline:
      processors:
        - group_by_value:
            value: ${! meta("kafka_partition") }
        - archive:
            format: binary

    output:
      aws_s3:
        bucket: ${S3_BUCKET}
        content_encoding: ""
        content_type: application/octet-stream
        credentials:
          id: ${AWS_ACCESS_KEY_ID}
          profile: ""
          role: ""
          role_external_id: ""
          secret: ${AWS_SECRET_ACCESS_KEY}
          token: ""
        endpoint: ""
        force_path_style_urls: false
        path: ${S3_PATH}
        region: ${AWS_REGION}
        timeout: 5s

Start by reproducing the reported failure with the provided Kafka input, pipeline, and aws_s3 output configuration on the referenced Benthos version. Trace the handling of the Kafka key through the S3 request and identify what produces the invalid X-Amz-Meta-Kafka_key header; done means the cause is established and the failure has a verified resolution.