I restarted the build for powerpc yesterday, and it did not run into reserved ports issue and build passed. I suspect that this is because the ppc64 build (which runs on the same builder 'blaauw' was not running in parallel and thus the two build jobs were not competing for the same ports on that host.
A later restart of ppc64 when the powerpc build had completed likewise did not run into reserved ports issues. Thus I'd say this is a Debian builder problem. The builds should be running inside a container or something so that they can't affect each other.
