When logging was disabled completely, performance under audit conditions was much improved exposing multiple crashes in different worker threads such as those performing garbage collection and logging.
This occurs using "Overlapped mode" in IIS which allows smoother transitions for websites whilst being recycled, but also will have multiple processes that can be starting,working or shutting down, or a combination. When this is disabled, performance drops, but the process no longer crashes.
Attached are the debugdiag analyses of crashes which occurred during performance testing.
The root cause is that unlinking memory segments occurs whilst other processes may be processing shared memory. We have seen multiple crashes where pool is not available any more that have not been reproducible, and this seems a likely explanation for these.