Getting _split_type_failure while splitting xml, not sure why but records are processed

[saif3r (A)]

Hello All,

Based on an advice from earlier post, I created a config responsible for splitting my xml into multiple events. It looks like this:

input {
	file {
		path => "/mnt/abc/*.xml"
		start_position => "beginning"
	}
}

filter {
	if [message] =~ /<BATCH.*$/ {
		xml { 
			source => "message" 
			target => "theXML" 
			store_xml => true 
		}
		split { 
			field => "[theXML][PANEL][0][DUT]" 
		}
		split { 
			field => "[theXML][PANEL][0][DUT][GROUP][0]" 
		}
		split { 
			field => "[theXML][PANEL][0][DUT][GROUP][0][GROUP]" 
		}
		split { 
			field => "[theXML][PANEL][0][DUT][GROUP][0][GROUP][TEST]" 
		}
	} 
	else {
		drop { }
	}
}

output {
	stdout {
	}
	elasticsearch {
		hosts => ["10.10.10.10:9200]
		index => "abc"
		http_compression => true
	}
}

And here's part of my xml (added line breaks for better view, usually it's single line):

<?xml version="1.0" encoding="UTF-8"?>
<BATCH TIMESTAMP="2019-03-04T07:28:42.208+01:00">
  <FACTORY NAME="PARIS" />
  <PRODUCT NAME="PRODUCT"/>
  <REFS SEQ_REF=""/>
  <PANEL ID="1" COMMENT="">
    <DUT ID="1111" COMMENT="">
      <GROUP NAME="Main">
        <GROUP NAME="First_Test_Group">
          <TEST NAME="Test_1"/>
          <TEST NAME="Test_1"/>
          <TEST NAME="Test_1"/>
          <TEST NAME="Test_1"/>
        </GROUP>
        <GROUP NAME="Main_2"/>
      </GROUP>
    </DUT>
  </PANEL>
</BATCH>

Here's the stdout output:

http://oneclickpaste.com/3401/

One record view from Kibana:

Logstash properly generated 5 events and put them into Elastic, but each event has a _split_type_failure and I'm not sure what might be the outcome later on. What am I doing wrong with my config? What should I change to make sure that data will be parsed properly?
Thanks in advance.

[Badger]

You should be seeing error messages in the logstash log

Only String and Array types are splittable. field:[theXML][PANEL][0][DUT][GROUP][0] is of type = Hash

This one only applies to Main_2

Only String and Array types are splittable. field:[theXML][PANEL][0][DUT][GROUP][0][GROUP][TEST] is of type = NilClass