This relates to https://github.com/elastic/beats/issues/6305 from what I can see.
Running 6.2.4 with the docker and system modules enabled. From the verbose log to console;
|2018-05-21T06:44:53.832+1000|INFO|template/load.go:73|Template already exists and will not be overwritten.|
|---|---|---|---|
|2018-05-21T06:45:02.896+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4|
|2018-05-21T06:45:02.896+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 6|
|2018-05-21T06:45:02.896+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 8|
|2018-05-21T06:45:02.897+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 9|
|2018-05-21T06:45:02.897+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 10|
|2018-05-21T06:45:02.898+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 17|
|2018-05-21T06:45:02.898+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 22|
|2018-05-21T06:45:02.899+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 27|
|2018-05-21T06:45:02.899+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 29|
|2018-05-21T06:45:02.899+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 44|
|2018-05-21T06:45:02.900+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 50|
|2018-05-21T06:45:02.900+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 292|
|2018-05-21T06:45:02.901+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 297|
|2018-05-21T06:45:02.901+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 298|
|2018-05-21T06:45:02.901+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 300|
|2018-05-21T06:45:02.902+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 515|
|2018-05-21T06:45:02.902+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 535|
|2018-05-21T06:45:02.902+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 537|
|2018-05-21T06:45:02.902+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 775|
|2018-05-21T06:45:02.903+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 884|
|2018-05-21T06:45:02.903+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 973|
|2018-05-21T06:45:02.903+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1007|
|2018-05-21T06:45:02.904+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1013|
|2018-05-21T06:45:02.904+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1027|
|2018-05-21T06:45:02.905+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1225|
|2018-05-21T06:45:02.905+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1226|
|2018-05-21T06:45:02.905+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1228|
|2018-05-21T06:45:02.906+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1278|
|2018-05-21T06:45:02.906+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1280|
|2018-05-21T06:45:02.907+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1282|
|2018-05-21T06:45:02.907+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1284|
|2018-05-21T06:45:02.908+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1289|
|2018-05-21T06:45:02.908+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1291|
|2018-05-21T06:45:02.908+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1293|
|2018-05-21T06:45:02.909+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1295|
|2018-05-21T06:45:02.909+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 1444|
|2018-05-21T06:45:02.915+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4009|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4169|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4170|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4171|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4172|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4173|
|2018-05-21T06:45:02.919+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4174|
|2018-05-21T06:45:02.920+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4175|
|2018-05-21T06:45:02.920+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4176|
|2018-05-21T06:45:02.920+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4177|
|2018-05-21T06:45:02.920+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4190|
|2018-05-21T06:45:02.920+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4191|
|2018-05-21T06:45:02.921+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4192|
|2018-05-21T06:45:02.921+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4193|
|2018-05-21T06:45:02.921+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4194|
|2018-05-21T06:45:02.921+1000|ERROR|process_summary/process_summary.go:79|Unknown state <73> for process with pid 4195|
(And there's more like that)
root@Tower:/mnt/user/beats/metricbeat-6.2.4-linux-x86_64/logs# uname -a
Linux Tower 4.14.40-unRAID #1 SMP PREEMPT Wed May 9 08:45:35 PDT 2018 x86_64 Intel(R) Celeron(R) CPU J1900 @ 1.99GHz GenuineIntel GNU/Linux
This is running on unRAID which isn't an officially supported OS, but it's linux under the hood so I thought I'd ask 
