make docker-build-kiali is using docker build -t ${DOCKER_TAG} _output/docker which is using caching. We are building kiali on build-kiali docker slave which is privileged container so it's using docker daemon on the host. Turns out it's very unreliable and cached layers can be used instead of actual build of kiali.

We need to make sure that it's not using caching. Maybe use dedicated VMs so it's properly isolated when running more build jobs concurrently and always use docker build --no-cache