diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35bf67a..5ccbe9f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -66,6 +66,14 @@ per the process in [`docs/releasing.md`](docs/releasing.md).
   `docker-proxy`, and `docker-control` previously fell back to Docker's uncapped default, so
   their logs could grow without bound and fill the disk on a long-running host (#123).
 
+### Fixed
+
+- `pithead backup` no longer aborts when `du`/`df` exit non-zero on an unreadable file or a
+  transient FS error — the disk-space pre-check now degrades gracefully (its "proceeding without
+  a space check" fallback was previously unreachable under `set -e`) (#127).
+- `pithead doctor` now exits non-zero when a critical check FAILS, so it can be used as a
+  cron/CI/monitoring health gate (it previously always exited 0); warnings alone still exit 0 (#127).
+
 ### Security
 
 - The monerod RPC credentials are no longer interpolated into the compose healthcheck command
diff --git a/pithead b/pithead
index 1ddc7f2..79cdb4b 100755
--- a/pithead
+++ b/pithead
@@ -371,6 +371,9 @@ doctor() {
     else
         log "All checks passed."
     fi
+    # Propagate a non-zero exit when any critical check FAILED, so `doctor` is usable as a health
+    # gate in cron/CI/monitoring (mirrors `status`). Warnings alone still exit 0 (#127).
+    [ "$DR_FAIL" -gt 0 ] && return 1
     return 0
 }
 
@@ -483,8 +486,12 @@ stack_backup() {
     # so we assume the archive needs roughly the source size plus a ~5% safety margin.
     local need_kb avail_kb
     # sudo: the Tor data dir is owned by 100:101; -c gives a grand total across all items.
-    need_kb=$(sudo du -sck "${items[@]}" 2>/dev/null | awk 'END{print $1}')
-    avail_kb=$(df -Pk "$backups_dir" 2>/dev/null | awk 'NR==2{print $4}')
+    # `|| true`: du exits non-zero if it can't read any descendant (a permission-denied subdir, a
+    # file vanishing mid-walk, an NFS hiccup) even though 2>/dev/null hides the message and a total
+    # is still printed. Without this, errexit (set -e) aborts the whole backup on a bare assignment,
+    # making the graceful "proceeding without a space check" fallback below unreachable (#127).
+    need_kb=$(sudo du -sck "${items[@]}" 2>/dev/null | awk 'END{print $1}') || true
+    avail_kb=$(df -Pk "$backups_dir" 2>/dev/null | awk 'NR==2{print $4}') || true
     if [ -n "$need_kb" ] && [ -n "$avail_kb" ]; then
         if [ "$avail_kb" -lt "$((need_kb + need_kb / 20))" ]; then
             local avail_gib=$((avail_kb / 1048576)) need_gib=$((need_kb / 1048576))
@@ -1743,7 +1750,7 @@ main() {
         upgrade)          require_deployed; stack_upgrade ;;
         logs)             require_env; log "Following logs (Ctrl+C to exit)..."; docker compose logs -f "$@" ;;
         status)           require_env; stack_status || exit 1 ;;
-        doctor)           doctor ;;
+        doctor)           doctor || exit 1 ;;
         reset-dashboard)  require_deployed; reset_dashboard "$@" ;;
         backup)           stack_backup "$@" ;;
         restore)          stack_restore "$@" ;;
diff --git a/tests/stack/run.sh b/tests/stack/run.sh
index 77045f6..add7a9a 100755
--- a/tests/stack/run.sh
+++ b/tests/stack/run.sh
@@ -350,6 +350,25 @@ REMOTE="tor=running:healthy monerod=missing p2pool=running:none tari=running:hea
 out="$(cd "$ST" && FAKE_STATES="$REMOTE" PATH="$ST/bin:$PATH" ./pithead status 2>&1)"; rc=$?
 assert_rc "status: remote mode ignores monerod" "$rc" "0"
 
+echo "== black-box: doctor exit code (#127) =="
+# doctor must EXIT NON-ZERO when a critical check fails, so it's usable as a cron/CI health gate
+# (it previously always returned 0). Drive one failure via an unreachable Docker daemon; jq/openssl
+# stay real on PATH so only the daemon check fails.
+DOC="$SANDBOX/doctor"; mkdir -p "$DOC/bin"; cp "$STACK" "$DOC/pithead"
+cat > "$DOC/bin/docker" <<'EOF'
+#!/usr/bin/env bash
+case "$*" in
+  "info") exit 1 ;;   # daemon unreachable -> doctor records a critical FAIL
+  *)      exit 0 ;;   # `--version`, `compose version`, etc. succeed
+esac
+EOF
+printf '#!/usr/bin/env bash\nexit 0\n' > "$DOC/bin/sudo"
+chmod +x "$DOC/bin/docker" "$DOC/bin/sudo"
+out="$(cd "$DOC" && PATH="$DOC/bin:$PATH" ./pithead doctor 2>&1)"; rc=$?
+assert_contains "doctor runs to the summary"          "$out" "Diagnostics summary"
+assert_contains "doctor flags the unreachable daemon" "$out" "Docker daemon is not reachable"
+assert_rc       "doctor exits 1 on a critical FAIL"   "$rc" "1"
+
 # ---------------------------------------------------------------------------
 echo ""
 printf 'pithead tests: \033[1;32m%d passed\033[0m, ' "$PASS"