I had an opposite experience with National a few weeks ago. Was driving on a suburban road when we heard a sound like we were dragging a branch under the car. Stopped and checked including under the hood but saw nothing obvious. Resumed driving, no noise but almost immediately got an alternator warning. Decided to stop again but before I could stop in a safe location, I was also getting a coolant temperature warning. OK, we have a serious problem. Once stopped, again opened the hood and immediately saw the coolant was boiling in its tank. Not good. Then noticed the broken serpentine belt. OK, this car has gone as far as it can go.

It's about 8:00 on a Saturday night (and on a personal level, not helped by having flown in red-eye that morning - we really were looking forward to getting to the hotel 30 minutes ahead). Called National and they were very responsive. Given it was Saturday night, the only replacement option was returning to the airport about 30 minutes away (in the wrong direction :-( ). They sent a tow truck (arrived in about an hour) and a text link to summon Uber (at their expense) to take us back to the airport. By the time the tow truck arrived, it was raining so he let us sit in the car until the Uber arrived. Back to the airport (only real hassle there was somehow Uber's driver app put the EWR rental car center on the wrong side of 1/9; OTOH, driving out I had noticed where there was a ride-share/private vehicle drop off area so was able to direct the driver to it). And even though National arranged the Uber, it matched the phone number to my Uber account so could see where the driver was while waiting). Anyway, replacement car obtained and on our way at a net cost of about 2.5 hours. Never heard anything further about it from National.