Sorry for the last reply, my newserver seems to have low retention. Your post disappeared before I saw it. I found it while googling for a solution the my problem.
About blamelessness, I was trying to avoid thinking that, but really, there doesn't seem to be a way to avoid wondering how it could have happened. The leak did not come out of the engine proper, but where the crank shaft enters the transmission. I'm not sure, but I suspect that securing this fitting is part of the installation of the replacement engine. So the engine might be fine, but perhaps the leak results from nonideal installation of the engine (frankly, I'm not sure about the details). Regardless of how it happened, it is still baffling how its sizable presence could have been missed over several visits for troubleshoot chemical & oil smells, and considering a steady oil loss. I'm quite happy with their willingness to fix it, but bothered by what this (and other discrepancies) implies about objectivity and reliability both of their troubleshooting and assessments. Hence, the uncertainty and the need to verify, or at least corroborate their assessment with other indicators and/or assessments.
T.O.