Openshift: Using `emptydir` (tmpfs) for cache breaks builds

In Openshift 4.11.46 using buildkitd v0.12 and fuse-overlayfs:

For performance reasons I tried to use tmpfs as buildkit cache:

   volumeMounts:
      - name: buildkitd-cache-mem
        mountPath: /home/user/.local/share/buildkit
    volumes:
      - name: buildkitd-cache-mem
        emptyDir:
          medium: Memory
          sizeLimit: 100Gi`

This leads to mysterious errors such as

11:39:51   > [stage-1 2/5] RUN dnf install tftp-server tftp -y &&     dnf clean all:
11:39:51  3.224 Error: Cannot rename directory "/var/cache/dnf/rpm-rhel8-codeready-remote-e1af419ca1d84a02/tmpdir.CRc2cz/repodata" to "/var/cache/dnf/rpm-rhel8-codeready-remote-e1af419ca1d84a02/repodata": cannot create directory /var/cache/dnf/rpm-rhel8-codeready-remote-e1af419ca1d84a02/repodata: File exists

which reproducibly go away when switching to a PVC.

Any thoughts on what might be causing this? Thanks

No source file or test is named. Start by reproducing the failure with the OpenShift 4.11.46, buildkitd v0.12, fuse-overlayfs, and emptyDir configuration, then compare it with the PVC case while examining the /home/user/.local/share/buildkit cache mount. Done means identifying why tmpfs produces the dnf rename error and documenting or validating a resolution.