Persistent queue in Logstash 6.1 causes problems with cef parsing

[Mugen (Lars)]

After enabling the persistent queue some of our cef logs could no longer be parsed.
The Logs semed to be split wrong.

The config looks as follows:

input {
   tcp {
     port => 5514
     type => "forti_log"
     codec => "cef"
  }
}


filter {
#The Fortigate syslog contains a type field as well, we'll need to rename that field in order for this to work
 if [type] == "forti_log" {

      grok{
          match => ["syslog", "%{SYSLOG5424PRI:syslog_index}%{SYSLOGTIMESTAMP:date} %{NOTSPACE:logsource}"]
      }




        kv {
    source => "message"
    value_split => "="
#Expects you have csv enable set on your Fortigate. If not I think you'll have to change it to " " but I didn't test that.
    field_split => " "
}

    mutate {

#The syslog contains a type field which messes with the Logstash type field so we have to rename it.
    rename => { "type" => "ftg_type" }
    rename => { "subtype" => "ftg_subtype" }
    add_field => { "type" => "forti_log" }
    convert => { "rcvdbyte" => "integer" }
    convert => { "sentbyte" => "integer" }
}

date {
    match => ["FTNTFGTeventtime", "UNIX" ]
    target => "FTNTFGTeventtime"
}

date {
    match => [ "date", "MMM dd HH:mm:ss" ]
    target => "@timestamp"
    }

     mutate {
 #add/remove fields as you see fit.
     remove_field => ["syslog_index","syslog","syslog5424_pri","path","service","date","time","sentpkt","rcvdpkt","log_id","poluuid"]
 }
}
}

Is this a known problem that could be solved with a simple upgrade of logstash?