Spinning up a build agent template that uses spot pricing appears to use the ID of an instance provisioned by a totally different spot request. e.g. 

Spot instance id in provision: sir-d29i7m7m
Mar 06, 2019 10:50:36 AM INFO hudson.plugins.ec2.EC2RetentionStrategy start
Start requested for jenkins-test-agent (sir-d29i7m7m)
Mar 06, 2019 10:50:36 AM INFO hudson.plugins.ec2.EC2Cloud log
Launching instance: i-0569a98d4e6447e66

In this example, instance i-0569a98d4e6447e66 is an instance fulfilled by a spot request created 1 hour prior. The spot instance provisioned by sir-d29i7m7m eventually starts but is untracked anywhere by Jenkins.

This is incredibly frustrating, because I'm ending up terminating totally unrelated instances because the config cannot be changed once the agent has been created and of course it cannot ssh in to instances created with an entirely different keypair.

I'm not sure how to debug this further, so would appreciate any advice in being able to provide more information or if this is a dupe.