When A Coin Is Minted...

I'm not sure of which is what all the time but one thing I've always noticed is the geatest amount of errors are on the obverse. I started asking dealers I know what that is and they all agreed that the main reason is the greatest amount of people just don't look closely at the reverses of coins. Many have little idea of what is on the reverses too. Try this. Ask the average person what the building is on the reverse of a Jefferson nickel. What is that on the back of the Roosevelt dime? Unless they are Numismatist, and many of them don't know either, you'll just get a blank stare as if who cares.
There may well be lots and lots of errors of all kinds on the reverses of coins, but who would notice?
Here is another reverse thing. Rotated reverses or are they rotated obverses? And even the famous Red Book on pages 400 and up don't mention Rotated reverses on coins. Do they exist?

By ancient tradition going right back to the invention of Western-style coinage, the obverse is always the anvil (lower die) side. As far as I'm aware, most countries still abide by this tradition.

They certainly are never "replaced randomly", otherwise we'd be seeing an awful lot more genuine two-headed and two-tailed coins. The shafts of obverse and reverse dies are completely different shapes, so they can't accidentally be inserted into the press on the wrong side.