diff --git a/4-seasons.sh b/4-seasons.sh
index 48a2582..7429505 100755
--- a/4-seasons.sh
+++ b/4-seasons.sh
@@ -95,34 +95,33 @@ trap cleanup EXIT
 
 mapfile -t all_images < <(find "$image_dir" -type f -name "*.jpg" | sort)
 
-# Validate each frame: skip empty files, corrupt JPEGs, and optionally grey/uniform frames.
-# SEASONS_GREY_STDDEV_MIN=0 (default) disables the grey filter.
-# Set to e.g. 5 in sky-cam.conf to drop uniform grey frames (bad-signal captures).
+# Validate each frame: skip empty files and optionally uniform-colour bad-signal frames.
+# SEASONS_GREY_STDDEV_MIN=0 (default) disables the content check entirely.
+# When enabled, large files (> SEASONS_LARGE_FRAME_BYTES, default 1 MB) are trusted
+# as good without running the expensive ImageMagick check — only sub-1MB frames
+# are inspected.  This keeps the filter fast even on days with 40k+ images.
 GREY_MIN="${SEASONS_GREY_STDDEV_MIN:-0}"
-GREY_DARK_FLOOR="${SEASONS_GREY_DARK_FLOOR:-30}"  # frames darker than this are never skipped
+GREY_DARK_FLOOR="${SEASONS_GREY_DARK_FLOOR:-30}"
+LARGE_BYTES="${SEASONS_LARGE_FRAME_BYTES:-1048576}"  # files above this skip content check
 images=(); bad=0; grey=0
 for img in "${all_images[@]}"; do
-    # Empty or unreadable
+    # Skip empty or unreadable files (0-byte writes from camera reconnects)
     if [ ! -r "$img" ] || [ ! -s "$img" ]; then
         echo "WARNING: skipping empty/missing frame: $(basename "$img")"
         ((bad++)) || true; continue
     fi
-    # Corrupt JPEG — ffprobe can't identify any video stream
-    if ! ffprobe -v quiet -select_streams v:0 \
-            -show_entries stream=codec_name -of csv=p=0 "$img" 2>/dev/null \
-            | grep -q .; then
-        echo "WARNING: skipping corrupt frame: $(basename "$img")"
-        ((bad++)) || true; continue
-    fi
-    # Optional: skip uniform-grey bad-signal frames.
-    # A frame is bad-signal if it is BOTH uniform (low stddev) AND not dark.
-    # Night frames are dark so they pass even with low stddev.
+    # Optional: skip uniform-colour bad-signal frames (green, grey, etc.).
+    # Only runs ImageMagick on files below SEASONS_LARGE_FRAME_BYTES — large files
+    # are always good and skip the check entirely.
     if [ "$GREY_MIN" != "0" ] && command -v convert &>/dev/null; then
-        read -r stddev mean < <(convert "$img" -colorspace Gray \
-            -format "%[fx:int(standard_deviation*255)] %[fx:int(mean*255)]" \
-            info: 2>/dev/null || echo "255 128")
-        if [ "${stddev:-255}" -lt "$GREY_MIN" ] && [ "${mean:-0}" -gt "$GREY_DARK_FLOOR" ]; then
-            ((grey++)) || true; continue
+        fsize=$(stat -c%s "$img" 2>/dev/null || echo 0)
+        if [ "$fsize" -lt "$LARGE_BYTES" ]; then
+            read -r stddev mean < <(convert "$img" -colorspace Gray \
+                -format "%[fx:int(standard_deviation*255)] %[fx:int(mean*255)]" \
+                info: 2>/dev/null || echo "255 128")
+            if [ "${stddev:-255}" -lt "$GREY_MIN" ] && [ "${mean:-0}" -gt "$GREY_DARK_FLOOR" ]; then
+                ((grey++)) || true; continue
+            fi
         fi
     fi
     images+=("$img")
diff --git a/README.md b/README.md
index 66d030a..090729c 100644
--- a/README.md
+++ b/README.md
@@ -234,6 +234,23 @@ Attribution data for every file is written to `sunrise-sounds/manifest.json`.
 ./4-seasons.sh east
 ```
 
+**Re-run a daily seasons clip** for a specific past date:
+```bash
+./4-seasons.sh east 2026-04-19
+```
+
+**Backfill multiple past dates** (useful after a camera outage or a fresh install with existing images):
+```bash
+for d in 2026-04-15 2026-04-16 2026-04-17 2026-04-18 2026-04-19; do
+    ./4-seasons.sh east "$d"
+done
+```
+
+Replace the date list with whatever range you need.  Each run produces one `*-final.mp4` in the movement's output directory.  Once all days for a movement are present you can build the montage manually:
+```bash
+./montage-mvt.sh east 2026-04-19   # date of the last day of that movement
+```
+
 **Rebuild a movement montage** (e.g. to retry audio after a failure):
 ```bash
 ./montage-mvt.sh east                   # uses today's date
diff --git a/daily_sunrise_video.sh b/daily_sunrise_video.sh
index c3076fa..bb0908a 100755
--- a/daily_sunrise_video.sh
+++ b/daily_sunrise_video.sh
@@ -356,10 +356,10 @@ if $step3b_ok; then
                 -name "*-daily-sunrise-test.mp4" \
                 -mtime +"$demo_retain" -print -delete 2>/dev/null | wc -l)
             [ "$deleted_demo" -gt 0 ] && \
-                echo "Demo retention: deleted $deleted_demo test file(s) older than ${demo_retain} days"
+                echo "Demo retention: deleted $deleted_demo test file(s) older than ${demo_retain} days" || true
         fi
     else
-        [ -f "${cam_audio:-}" ] && rm -f "${cam_audio:-}"
+        [ -f "${cam_audio:-}" ] && rm -f "${cam_audio:-}" || true
         "$SCRIPT_DIR/notify.sh" "Sunrise ready: $current_date" \
             "$(basename "$final_video") — ${actual_dur}s, sunrise at ${SR_TIME} | $final_video" || true
 
@@ -370,7 +370,9 @@ if $step3b_ok; then
                 -path "*/sunrise-only/*-daily-sunrise.mp4" \
                 -mtime +"$retain" -print -delete 2>/dev/null | wc -l)
             [ "$deleted_old" -gt 0 ] && \
-                echo "Retention: deleted $deleted_old sunrise video(s) older than ${retain} days"
+                echo "Retention: deleted $deleted_old sunrise video(s) older than ${retain} days" || true
         fi
     fi
 fi
+
+exit 0
diff --git a/sky-cam.conf b/sky-cam.conf
index ed9d92b..597a8b1 100644
--- a/sky-cam.conf
+++ b/sky-cam.conf
@@ -256,18 +256,23 @@ ENCODE_PRESET=slow       # ffmpeg preset for all encodes (slow/medium/fast)
 AUDIO_BITRATE=192k       # montage-mvt.sh           — music track on movement montages
 
 # ── Frame validation (4-seasons.sh) ──────────────────────────────────────────
-# Corrupt or empty frames (e.g. first frame after a camera reconnect) are always
-# skipped automatically via ffprobe.  No config needed.
+# Empty (0-byte) frames are always skipped.  No config needed for that.
 #
 # SEASONS_GREY_STDDEV_MIN / SEASONS_GREY_DARK_FLOOR — optional bad-signal filter.
+# Catches uniform-colour frames caused by a bad RTSP signal: solid green, grey, etc.
+# These are valid JPEGs but contain no real image content.
 # Uncomment both lines to enable.  A frame is dropped only when BOTH are true:
 #   1. pixel standard deviation (0–255) < SEASONS_GREY_STDDEV_MIN  (frame is uniform)
 #   2. mean brightness (0–255)          > SEASONS_GREY_DARK_FLOOR  (frame is not dark)
-# This keeps genuine night frames (dark + low variation) while dropping
-# solid-grey bad-signal frames (mid-bright + no variation).
+# Night frames are dark so they always pass even if stddev is low.
 # Requires ImageMagick (convert).  Start with these values and tune from there:
-#SEASONS_GREY_STDDEV_MIN=5    # skip if stdev < 5 (very uniform)
+#SEASONS_GREY_STDDEV_MIN=5    # skip if stdev < 5 (very uniform colour)
 #SEASONS_GREY_DARK_FLOOR=30   # …but only if mean brightness > 30 (not a night frame)
+#
+# Performance: ImageMagick is only called on files below SEASONS_LARGE_FRAME_BYTES.
+# Files above that threshold are always good and skip the check entirely.
+# Default 1 MB — adjust if your camera produces larger bad-signal frames.
+#SEASONS_LARGE_FRAME_BYTES=1048576
 
 # ── Montage attribution overlay ───────────────────────────────────────────────
 # A translucent bar across the top of each movement montage, naming the