Today, we noticed that the sbuild toolchain on tools-package-builder-02 seems to have developed some kind of bug. It cannot chown the chroot to <user>:sbuild. This is strange because the only place that doesn't work when done directly by hand is on an NFS dir, and the build dir should be on the instance disk.
For testing and comparison, I built a new tools-package-builder-03 using buster (and no NFS at all--so changing at least 10 variables in terms of build toolchain), and that seems to be happier except that the autotest/m4-based testsuite attached to toollabs completely fails. The latter may have been something silly I did as well, but you never know. I have not tried rebuilding the stretch version, partly because it was showing some odd issues like the pins no longer being valid (partly because the upstream module pins everything to stretch-backports).