2 of 10 Tags dont work - any ideas?

Hi,

I just got 10 RFID tags and put them in 10 identical boxes. Then downloaded TeddyBench, converted some stuff and assigned it to the tags. 8 of them play correctly and I didnt get an error, but with two of them, the box says that it doesnt have an internet connection (of course not!) and gives the code “Schildkröte”/turtle. In addition to that, the box deletes the content that was originally matched with this tag. So when putting the microsd card back in the computer, the audio file for the “error tag” isnt there any more.

The workflow for every single tag was the same and I made a screenshot for all of them from my NFC tool when reading the UID, so I can as well ensure that the assigned tag is correct.

Any ideas? Are the RFID tags defect?