I'm tracking issue which is currently the biggest distill blocker for RHEL-6. This issue is currently happening in pungi-4 as well.
Basically RHEL-6boot iso is altered in further phases outside createiso, as far as I'm aware this is not happening with lorax, so fedora/rhel-7 are safe.
Proposing fix to move checksum calculation to later phase, and write a checkum test into a test phase.
Referencing https://bugzilla.redhat.com/show_bug.cgi?id=1238953
Checksums are now computed in a separate phase (as result of #31).
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/pungi/pungi/issues/35
Please continue any further discussion there.