I assume these are parent pom's right?
Are they part of the reactor or are they poms from a remote repository?
The order of resolving parents has changed a bit: it used to look in the cache based on GAV, followed by matching the path of this modelSource.
Now it is kind of the other way around: look in cache by relativePath or read by relativePath, next match the GAV.
Were these poms generated?
They're "tiles" - using our tiles-maven-plugin to provide mixin support, essentially they do get injected as parents into the model tho.
We read the tile.xml artefact we publish/manually write and inject that as parents.