Varnish Cache Plus is a high-performance web accelerator and may be difficult to get a handle on initially.
There are a lot of forums and pages offering Varnish help. Here are some we find useful:
Varnish Cache Plus is normally quite stable. There should not be any panics in normal usage.
As backend behavior and client loads are not easily simulated and tested, sometimes Varnish ends up in a state where it recognizes that it should not be. In those cases Varnish will perform a controlled panic, syslog what went wrong, and restart. This output contains useful information on what happened.
In cases where this is not written to syslog on a crash, support can offer guidance on how to extract it from core dumps.
Contact Varnish Software support on email.
Often support will ask you for a varnishgather data collection. If you run this script and send that on the initial request, support will be able to help you sooner.