diff --git a/app/decoder.py b/app/decoder.py
index e17b8a2..7a46838 100644
--- a/app/decoder.py
+++ b/app/decoder.py
@@ -299,8 +299,11 @@ def parse_advertisement(
     timestamp = int.from_bytes(payload[32:36], byteorder="little")
     flags = payload[100]
 
-    # Parse flags
+    # Parse flags — clamp device_role to valid range (0-4); corrupted
+    # advertisements can have junk in the lower nibble.
     device_role = flags & 0x0F
+    if device_role > 4:
+        device_role = 0
     has_location = bool(flags & 0x10)
     has_feature1 = bool(flags & 0x20)
     has_feature2 = bool(flags & 0x40)
diff --git a/app/models.py b/app/models.py
index 52fa989..96615c2 100644
--- a/app/models.py
+++ b/app/models.py
@@ -4,6 +4,10 @@ from pydantic import BaseModel, Field
 
 from app.path_utils import normalize_contact_route, normalize_route_override
 
+# Valid MeshCore contact types: 0=unknown, 1=client, 2=repeater, 3=room, 4=sensor.
+# Corrupted radio data can produce values outside this range.
+_VALID_CONTACT_TYPES = frozenset({0, 1, 2, 3, 4})
+
 
 class ContactRoute(BaseModel):
     """A normalized contact route."""
@@ -59,16 +63,30 @@ class ContactUpsert(BaseModel):
                 -1 if radio_data.get("out_path_len", -1) == -1 else 0,
             ),
         )
+        # Clamp invalid contact types to 0 (unknown) — corrupted radio data
+        # can produce values like 111 or 240 that break downstream branching.
+        raw_type = radio_data.get("type", 0)
+        contact_type = raw_type if raw_type in _VALID_CONTACT_TYPES else 0
+
+        # Null out impossible coordinates — the contact is still ingested,
+        # but garbage lat/lon (e.g. 1953.7) is discarded rather than stored.
+        lat = radio_data.get("adv_lat")
+        lon = radio_data.get("adv_lon")
+        if lat is not None and not (-90 <= lat <= 90):
+            lat = None
+        if lon is not None and not (-180 <= lon <= 180):
+            lon = None
+
         return cls(
             public_key=public_key,
             name=radio_data.get("adv_name"),
-            type=radio_data.get("type", 0),
+            type=contact_type,
             flags=radio_data.get("flags", 0),
             direct_path=direct_path,
             direct_path_len=direct_path_len,
             direct_path_hash_mode=direct_path_hash_mode,
-            lat=radio_data.get("adv_lat"),
-            lon=radio_data.get("adv_lon"),
+            lat=lat,
+            lon=lon,
             last_advert=radio_data.get("last_advert"),
             on_radio=on_radio,
         )
diff --git a/app/radio_sync.py b/app/radio_sync.py
index cdedc31..4d769a3 100644
--- a/app/radio_sync.py
+++ b/app/radio_sync.py
@@ -21,7 +21,7 @@ from meshcore import EventType, MeshCore
 from app.channel_constants import PUBLIC_CHANNEL_KEY, PUBLIC_CHANNEL_NAME
 from app.config import settings
 from app.event_handlers import cleanup_expired_acks, on_contact_message
-from app.models import Contact, ContactUpsert
+from app.models import Contact, ContactUpsert, _VALID_CONTACT_TYPES
 from app.radio import RadioOperationBusyError
 from app.repository import (
     AmbiguousPublicKeyPrefixError,
@@ -1073,7 +1073,6 @@ async def sync_contacts_from_radio(mc: MeshCore) -> dict:
         # Import radio-favorited contacts into app favorites.
         # Only trust the favorite bit on contacts with a valid type (0-4);
         # garbled radio data can have junk flags with bit 0 set.
-        _VALID_CONTACT_TYPES = {0, 1, 2, 3, 4}
         radio_fav_keys = [
             pk
             for pk, data in contacts.items()