That's weird... I've actually tested all these QR using my phone before uploading and just now and all of them worked, and one of these codes, the one with "POA" on, is used in a real event in my school and most people can scan them properly...
I suspect that you're using a not-that-strong QR scanner, in China we mainly use the QR code scanner in Wechat, which is quite powerful. I usually get a correct result when I scan the QR with Wechat, but my phone's built-in scanner and Facebook app's scanner would fail to recognize it sometimes and also numerous online recognizer failed to recognize it at all... A small trick is to vibrate your phone a bit when scanning, sometimes it would help the phone scanner to locate the QR. (Have a try~ maybe it would work this time~)
I'm aware that this form of QR is more fragile than normal QR so I suggested that "the dimension of the QR code is best in the range of [25,50]", but it seems that it is just a bit too hard for average QR scanners even if the size is in this range :(
