Using a custom build record directory means that artifacts are lost when renaming a matrix project.

I have set up:
Build Record Root Directory d:/artifacts/${ITEM_FULL_NAME}/builds/

And a matrix job: "Rename_test" which has one user-defined axis "FOO" with one value "bar".
which executes a Windows batch command: "echo %BUILD_TAG% > afile.txt"
And Archives the artifact afile.txt.

I run this a couple of times to create some artifacts then rename the job to "Rename_test_new_name". The artifacts (and other per-configuration build data) are not moved so the folder: d:/artifacts now has "Rename_test" and "Rename_test_new_name". New artifacts are created in the new name, old artifacts are still in the old folder.

I think that this may be to do with how ITEM_FULL_NAME works. With the default "Build record root directory" (${ITEM_ROOTDIR}/builds) the per configuration data is stored in:
Rename_test/configurations/axis-FOO/bar/builds

With the build record root directory changed to "d:/artifacts/${ITEM_FULL_NAME}/builds/" they are stored in:
Rename_test/FOO=bar/builds