Decided it was time I set this up in addition to periodically doing a full yum update. It was failing and the output is truncated in Systems Manager, writing the logs to S3 did not help much either. Finally looked at /var/log/messages and between various amazon-ssm-agent lines a bunch familiar looking kernel message related to oom-killer.
The python2.7 script executed as part of patch manager takes nearly a whopping 400MB of ram to run.
By the way python 2 is finally dead according to the python peoples. https://www.python.org/doc/sunset-python-2/
Reduced the amount of Apache threads my little web server was running to free up some memory for this hog.