Have you used the online service (running an older version of hcxpcapngtool):
https://hashcat.net/cap2hashcat/
or hcxpcapngtool from git?
At the moment, I don't know why your hash file is damaged. Usually this could happen by editing it (search and replace function of the editor) by sed, by awk or by grep, but this is not the case, because you haven't edited it.
It also could happen during the download of the hash file from the online converter, if you use this service.
To make sure that it isn't a bug in hcxpcapngtool (that would be ugly, because I just released v 6.2.7):
Can I have the original cap file please?
https://hashcat.net/cap2hashcat/
or hcxpcapngtool from git?
At the moment, I don't know why your hash file is damaged. Usually this could happen by editing it (search and replace function of the editor) by sed, by awk or by grep, but this is not the case, because you haven't edited it.
It also could happen during the download of the hash file from the online converter, if you use this service.
To make sure that it isn't a bug in hcxpcapngtool (that would be ugly, because I just released v 6.2.7):
Can I have the original cap file please?