I can recreated this issue, the root cause is after umount called, it return 0, but the mounted dev is not released, the resource is still in busy status, so we can add more sleep before the 'rmdir' command call.
I can recreated this issue, the root cause is after umount called, it return 0, but the mounted dev is not released, the resource is still in busy status, so we can add more sleep before the 'rmdir' command call.