diff --git a/backend/services/backup_destination_service.py b/backend/services/backup_destination_service.py
index c375594..8bcaff4 100644
--- a/backend/services/backup_destination_service.py
+++ b/backend/services/backup_destination_service.py
@@ -221,7 +221,11 @@ _NFS_VOLUME_PREFIX = "stackpilot-nfs-dest-"
 
 
 def _nfs_check_name(name: str) -> None:
-    if not name or "/" in name or name in (".", "..") or name.startswith(".."):
+    import re
+
+    # Same safe charset as the subdir parts: the name is interpolated into the
+    # helper container's shell commands.
+    if not name or not re.fullmatch(r"[A-Za-z0-9._-]+", name) or name.startswith("."):
         raise DestinationError(f"Invalid backup file name '{name}'")
 
 
@@ -308,7 +312,7 @@ def _nfs_run(volume: str, command: list[str]) -> str:
         raise DestinationError(f"NFS mount failed: {exc}") from exc
 
 
-def _nfs_helper(volume: str):
+def _nfs_helper(volume: str, command: list[str] | str = "true"):
     """A created (not started) helper container for archive I/O on /nfs."""
     import docker.errors
 
@@ -322,7 +326,7 @@ def _nfs_helper(volume: str):
         return safe_call(
             client.containers.create,
             settings.BACKUP_HELPER_IMAGE,
-            command="true",
+            command=command,
             volumes={volume: {"bind": "/nfs", "mode": "rw"}},
         )
     except (docker.errors.APIError, DockerError) as exc:
@@ -337,13 +341,23 @@ def _nfs_upload(dest: BackupDestination, cfg: dict, local_path: str, filename: s
     target = _nfs_target(cfg)
     # Creates the subdir if needed AND fails early with a clear mount error.
     _nfs_run(volume, ["mkdir", "-p", target])
-    container = _nfs_helper(volume)
+    # Unpack into the container's own filesystem, then copy the file across:
+    # extracting straight into the NFS mount makes the daemon chown the file,
+    # which a root_squash export refuses ("failed to Lchown ... for UID 0").
+    container = _nfs_helper(
+        volume, ["sh", "-c", f"cat '/tmp/{filename}' > '{target}/{filename}'"]
+    )
     try:
         with tempfile.TemporaryFile() as tmp:
             with tarfile.open(fileobj=tmp, mode="w") as tar:
                 tar.add(local_path, arcname=filename)
             tmp.seek(0)
-            container.put_archive(target, tmp)
+            container.put_archive("/tmp", tmp)
+        container.start()
+        status = container.wait(timeout=3600).get("StatusCode", 1)
+        if status != 0:
+            err = (container.logs(stdout=True, stderr=True) or b"").decode("utf-8", "replace")
+            raise DestinationError(f"NFS upload failed: {err.strip() or f'exit {status}'}")
     except docker.errors.APIError as exc:
         raise DestinationError(f"NFS upload failed: {exc}") from exc
     finally:
diff --git a/backend/services/stack_assets_service.py b/backend/services/stack_assets_service.py
index 8362a31..ced1216 100644
--- a/backend/services/stack_assets_service.py
+++ b/backend/services/stack_assets_service.py
@@ -94,6 +94,54 @@ def _split(path: str) -> tuple[str, str]:
     return os.path.dirname(clean) or "/", os.path.basename(clean)
 
 
+def _is_chown_error(exc: Exception) -> bool:
+    text = str(exc)
+    return "chown" in text.lower() and "not permitted" in text.lower()
+
+
+def _put_archive(container, dest: str, src_file: str, volumes: dict) -> None:
+    """Unpack an archive into a container path, coping with squashed mounts.
+
+    The daemon restores ownership while extracting, which an NFS/CIFS export
+    with ``root_squash`` refuses. In that case the archive is unpacked into a
+    throwaway container's own filesystem first and the files are then copied
+    across — ownership cannot be preserved there, but the restore completes
+    instead of failing outright.
+    """
+    with open(src_file, "rb") as fh:
+        try:
+            container.put_archive(dest, fh)
+            return
+        except Exception as exc:  # noqa: BLE001
+            if not _is_chown_error(exc):
+                raise
+    logger.warning("%s rejects ownership changes; restoring without it", dest)
+    client = get_client()
+    staging = _create_helper_with(
+        client, volumes, ["sh", "-c", f"cp -R /tmp/. '{dest}/'"]
+    )
+    try:
+        with open(src_file, "rb") as fh:
+            staging.put_archive("/tmp", fh)
+        staging.start()
+        status = staging.wait(timeout=3600).get("StatusCode", 1)
+        if status != 0:
+            err = (staging.logs(stdout=True, stderr=True) or b"").decode("utf-8", "replace")
+            raise AssetError(err.strip() or f"copy failed (exit {status})")
+    finally:
+        _remove(staging)
+
+
+def _create_helper_with(client, volumes: dict, command: list[str]):
+    ensure_helper_image(client)
+    return safe_call(
+        client.containers.create,
+        settings.BACKUP_HELPER_IMAGE,
+        command=command,
+        volumes=volumes,
+    )
+
+
 def inspect_paths(paths: list[str]) -> dict[str, dict]:
     """Classify host paths ({path: {"kind", "size"}}) via one helper container.
 
@@ -179,12 +227,12 @@ def import_path(source: str, kind: str, src_file: str) -> None:
     ensure_helper_image(client)
     if kind == "file":
         parent, _base = _split(source)
-        container = _create_helper(client, {parent: {"bind": "/dst", "mode": "rw"}})
+        mounts = {parent: {"bind": "/dst", "mode": "rw"}}
     else:
-        container = _create_helper(client, {source: {"bind": "/dst", "mode": "rw"}})
+        mounts = {source: {"bind": "/dst", "mode": "rw"}}
+    container = _create_helper(client, mounts)
     try:
-        with open(src_file, "rb") as fh:
-            container.put_archive("/dst", fh)
+        _put_archive(container, "/dst", src_file, mounts)
     finally:
         _remove(container)
 
@@ -225,10 +273,10 @@ def import_volume(full_name: str, labels: dict, src_file: str, wipe: bool = True
             volumes={full_name: {"bind": "/v", "mode": "rw"}},
             remove=True,
         )
-    container = _create_helper(client, {full_name: {"bind": "/v", "mode": "rw"}})
+    mounts = {full_name: {"bind": "/v", "mode": "rw"}}
+    container = _create_helper(client, mounts)
     try:
-        with open(src_file, "rb") as fh:
-            container.put_archive("/v", fh)
+        _put_archive(container, "/v", src_file, mounts)
     finally:
         _remove(container)
 
diff --git a/backend/version.py b/backend/version.py
index 0cfe496..c57694b 100644
--- a/backend/version.py
+++ b/backend/version.py
@@ -1,3 +1,3 @@
 """Single source of truth for the StackPilot release version."""
 
-APP_VERSION = "0.40.1"
+APP_VERSION = "0.40.2"
diff --git a/frontend/package.json b/frontend/package.json
index 00078ec..a8a22c2 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -1,7 +1,7 @@
 {
   "name": "stackpilot-frontend",
   "private": true,
-  "version": "0.40.1",
+  "version": "0.40.2",
   "type": "module",
   "scripts": {
     "dev": "vite",