Thanks for the help and testing.
In case anyone else was wondering what this was, it was a false alarm. The kern.log revealed the oom-killer (out of memory killer) was invoked by the kernel. It had shut down the webwork2 service to save the system when memory was low. The thing it needed was either more memory or reducing workers in conf/webwork2.mojolicious.yml from the default of 25.
In case anyone else was wondering what this was, it was a false alarm. The kern.log revealed the oom-killer (out of memory killer) was invoked by the kernel. It had shut down the webwork2 service to save the system when memory was low. The thing it needed was either more memory or reducing workers in conf/webwork2.mojolicious.yml from the default of 25.