Thanks for your reply. Yes I used a clean Ubuntu 22.04 system in a VM.
I started with a vanilla Ubuntu 22.04 VM running on QEMU/KVM (virt-manager)
It's very possible that the 4.1.5 builds and below failed because of an issue with my local environment. But the 4.1.6 and 4.1.7 builds failing with error 1 are I believe due to the MK3 build process including the build date in the build file which causes the make repro to fail with error 1
make repro
to fail witherror 1