Zipcar Take 3

I used the Zipcar for the 3rd time this morning. The second time was a week ago. We had a problem, the zipcard could not unlock the zipcar (Element Estelle) (all cars are alliteratively named for their models.
Fortunately when I called, they were able to unlock the adjacent car for me (Matrix McKenna), which I then took with only a few minute delay. Today I signed up for the second car (the Matrix), figuring it worked last time and the first did not. That was a wise choice, as someone else had reserved the other car this morning and had exactly the same problem I did previously, his card could not unlock Element Estelle. I realize Zipcar will do something for you (I am not clear what they will do), but this is a bad sign in general. Of my four interactions with zipcars, (three of my own and one observed for the other poor soul), two did not work correctly.