We recently discovered our build scripts weren't honoring release tags when checking out upstream projects code...
This means we were always building the latest code of an upstream project instead of the tagged releases.
Thankfully we only recently started building released versions of upstream projects and the impact was small. Unfortunately that means we've been hard at work updating our build scripts and starting new builds of our Docker containers.
Given we didn't receive any bug reports we're going to assume this didn't cause anyone great pain.
That said, this was an unfortunate lesson to learn the hard way and we will be keeping a closer eye on our build scripts going forward.