On windows, the wininit.exe process can't be accessed by the service (some machines .. EC2 specifically with DataCenter edition 2016 server), which can only be detected by turning on debug logging.
Logs look totally normal (other than lack of json post ops), but elastisearch shows nothing except the very first poll operation.. system goes totally silent.
Disabling the process metricset[s] within system module resumes normal data dispatch routine.
Took a solid hour or so to figure this out.
Figured someone should know about it.