Hello!
I was encountering the issue where I couldn't extract the .jpa archive, getting the error message about the archive headers a few seconds after Starting the extraction.
I did try all know possible troubleshooting steps - also went through this: https://www.akeeba.com/documentation/akeeba-kickstart-documentation/kscantextract.html
Nothing worked!
Finally, I realised what was wrong in my case and it was more obvious than expected.
I was moving via terminal (later via FTP, and URL Import) a .jpa archive of the newly developed WP website located on another cPanel account on the same server, to the original cPanel account, where there was sitting the old website.
The old website was a Joomla 1.5 instance and it was running on PHP 5.4.
After moving the .jpa file, I was running the kickstart.php script. The case is that it never came into mind at that point to check and switch the PHP version of the account to a newer PHP 8.1.
Kickstart.php 8.x was running without errors for the first steps on PHP 5.4 - but it was failing during the extraction, but there was no visible/obvious notice.
I realised due the error.log that was generated by PHP.
Now, switched to PHP 8.1 and everything worked.
So, I came here to give this notice... The kickstart documentation mentions the requirements, but the documentation page linked from the failing extraction page of kickstart has no reference. So, someone facing a similar issue might go through all troubleshooting steps without success.
Now, you would tell me... who in the world will ever try to run kickstart 8.x on PHP 5.4 and would be almost right... but hey, hey ... here I am (lol).
Anyway, you may want to add on top of the troubleshooting guide for issues with kickstart extractor the notice regarding checking system requirements, as friendly notice to anyone who might be dealing with similar problems. If the environment does not meet the minimum requirements, the script will not work.
*Strangely, kickstart.php didn't give any signs before starting the extraction though.
Have a good day!