On Mac OS you can run the debug build as well. Install gdb if it is not installed.
log file should be at /opt/lsws/logs/error.log stderr.log
You can ignore error message regarding mpstat.
The backtrace from a core file is more important, log file can help sometimes, send us the log file if need.
If a request crashes the server, browser will retries a few times, that's why you see them in cluster sometimes.
You can have a vhost discounted to a listener, just "Instantiate" the vhost from template, then remove the listener to vhost mapping from the listener configuration.
You can create a listener listen on private IP for internal test, and map VH to that listener.