You can install our site as a web app on your iOS device by utilizing the Add to Home Screen feature in Safari. Please see this thread for more details on this.
Note: This feature may not be available in some browsers.
Note that my wife and I have the same phones, but hers fails more often. But she has the magic touch with technological things—they tend to fail for her (unless I'm watching).
Here's a demo of this problem. Note that her problem with her card was that she was holding it in the wrong place (misled by a sticker I have on the window). Partly her phone key may fail because it's in her purse. When she takes it out, she tends to wave it around (makes a difference?).