Hi mickjoebill
Over discharge can be identified with a proper diagnostic charger.
I think the over discharge is identified, that is why they replaced the batteries so many times. I think TURIN gave the most likely explanation for this also.
Where things have gone wrong (re: 150 batteries changed in service) is the operators have not really ensured that the people at the sharp end are thoroughly briefed as to the consequences of EG. Leaving the towing switch on.