I worked a few years on the other side of the audit... almost all of the auditors I came across were 'new' and really did not know the tax laws that well... Most of the times it was teaching them what to look at...
I did get one who did estates.... we kept going back and forth on some points that I had all the backup... he finally said that he needed to get 'something', so I could choose what I was willing to 'give up'... since it was cheaper to give in than fight (for the taxpayer), we gave up something that was clearly ours just so we could take advantage of some better savings on some that we not so clear....
BTW, I was involved with one of the random audits back when they used to do them.. it was a split year return as the husband had died... they owned lots of real estate, oil wells, banks, etc. etc... about $2 mill in income back in the mid 80s... the guy could not find a single thing wrong with the return even though income had to be split and the return was probably 200 pages. With a random audit, they must check EVERYTHING... so every number had to have backup... it took him a couple of weeks to do it and it took me probably 40 hours to show him all the stuff...