Great first posts!
If a delivery center is handling over 100 cars a day, it is totally understandable that a few new owners would not have a good experience.
Generally, almost all online businesses have a roughly 5% problem rate - it more or less doesn't matter what you're selling or how.
Go to almost any product selling on Amazon and look at the 1-star reviews. Nearly every product has at least a couple of them. Doesn't mean that the product is bad - it just means that it's typical of anyone doing business at a distance.
My wife and I ran an online business (selling little model buildings to people who play table-top games!) - and we were INSANELY careful about having good customers. We had 95% 5-stars and 5% 1-star reviews - just like everyone else. Problems occur at every step - and many of them aren't yours.
We had a package we sent from Texas to Malaysia - we did everything right - but the customer ignored the requests to go to their post office an pay customs/import duty...so the entire package got returned to us about 6 months later. The cardboard box was COVERED with stickers from a dozen different customs, shippers and post offices - it had 3" rips in the cardboard and was so battered, that it looked more like a football than a shipping box! The product inside was smashed to hell - so we had to re-manufacture and re-ship the entire bundle - we put a couple of 'freebie' extra models in for him with a note explaining and apologizing for the delay. It finally got to the end customer in perfect condition - but 6 months late...and the bastard gave us a 1-star review for slow shipping!
Now - that said - we did make genuine mistakes - but still, 5% is a good number for how many transactions will go sufficiently wrong to get you a 1-star.
We never once got a 2, 3 or 4 star review. It was either "You guys are GODS and CAN DO NO WRONG!!!" or "Your product is total and utter *sugar* and your customer service is horrible!"...never anything in between.
So - I figure that if a delivery center handles 100 cars a day - there are going to be somewhere around 5 "oopsies" per day. Those people will blast social media with grief...presuming that their experience is typical.