Greetings @joejankowiak,
I just did a build myself to double-check this. For me the file had the proper extension attached. That is to say I can’t seem to reproduce this myself. Also on our internal automated builds, this file with the extension seems to be generated properly as well.
This sounds somewhat similar to this other thread here: Torizon-core-docker-apalis-imx8.ota.tar.zst gets truncated
Though the user in this thread never really figured out what the original problem was.
Best Regards,
Jeremias