diff --git a/proxy_chain_manager/app.py b/proxy_chain_manager/app.py
index b289404..ea0e913 100644
--- a/proxy_chain_manager/app.py
+++ b/proxy_chain_manager/app.py
@@ -111,7 +111,9 @@ def main() -> None:
     # HELPERS
     # ─────────────────────────────────────────────────────────────────────────
     def _btn(parent: Any, label: str, cmd: Any, w: int = 80, h: int = 28, **kw: Any) -> ctk.CTkButton:
-        # Pop styling keys so they are never duplicated in **kw (CustomTkinter raises on duplicate font, etc.).
+        # Pull known keys out first so **kw never duplicates CTkButton parameters (font, width, …).
+        kw.pop("text", None)
+        kw.pop("command", None)
         font = kw.pop("font", (FONT, 11))
         fg_color = kw.pop("fg_color", ACCENT)
         hover_color = kw.pop("hover_color", ACCENT2)
@@ -669,7 +671,7 @@ def main() -> None:
     ).pack(side="left")
 
     ctk.CTkFrame(sf_outer, fg_color="transparent", height=4).pack()
-    _btn(sf_outer, "💾  Save All Settings",
+    _btn(sf_outer, "Save All Settings",
          lambda: _save_settings(verbose=True), w=220, h=36,
          font=(FONT, 13)).pack(anchor="w", padx=6, pady=8)
 
diff --git a/proxy_chain_manager/config.py b/proxy_chain_manager/config.py
index ab5495a..cc30cc2 100644
--- a/proxy_chain_manager/config.py
+++ b/proxy_chain_manager/config.py
@@ -75,6 +75,63 @@ class Settings:
         return app_data_dir() / "settings.json"
 
 
+def sanitize_settings(s: Settings) -> tuple[Settings, bool]:
+    """Clamp invalid values from hand-edited JSON. Returns (settings, changed)."""
+    changed = False
+    try:
+        cl = int(s.chain_length)
+        if not (1 <= cl <= 8):
+            s.chain_length = max(1, min(8, cl))
+            changed = True
+    except (TypeError, ValueError):
+        s.chain_length = 3
+        changed = True
+    try:
+        p = int(s.local_port)
+        if not (1 <= p <= 65535):
+            s.local_port = max(1, min(65535, p))
+            changed = True
+    except (TypeError, ValueError):
+        s.local_port = 18888
+        changed = True
+    try:
+        if int(s.health_check_seconds) < 10:
+            s.health_check_seconds = 10
+            changed = True
+    except (TypeError, ValueError):
+        s.health_check_seconds = 180
+        changed = True
+    try:
+        if int(s.full_refresh_seconds) < 60:
+            s.full_refresh_seconds = 60
+            changed = True
+    except (TypeError, ValueError):
+        s.full_refresh_seconds = 1800
+        changed = True
+    try:
+        if int(s.validation_concurrency) < 1:
+            s.validation_concurrency = 1
+            changed = True
+    except (TypeError, ValueError):
+        s.validation_concurrency = 64
+        changed = True
+    try:
+        if int(s.max_candidates) < 10:
+            s.max_candidates = 10
+            changed = True
+    except (TypeError, ValueError):
+        s.max_candidates = 400
+        changed = True
+    try:
+        if float(s.validation_timeout_seconds) < 2.0:
+            s.validation_timeout_seconds = 2.0
+            changed = True
+    except (TypeError, ValueError):
+        s.validation_timeout_seconds = 12.0
+        changed = True
+    return s, changed
+
+
 def normalize_listen_host(s: Settings) -> tuple[Settings, bool]:
     """Force loopback bind so LAN/DHCP IP changes (e.g. cloned VMs) never break the listener."""
     if s.local_host == LISTEN_HOST:
@@ -103,7 +160,9 @@ def load_settings() -> Settings:
         s.pinned_chain = []
     if not hasattr(s, "manual_exit_proxy") or not isinstance(s.manual_exit_proxy, str):
         s.manual_exit_proxy = ""
-    s, changed = normalize_listen_host(s)
+    s, ch1 = sanitize_settings(s)
+    s, ch2 = normalize_listen_host(s)
+    changed = ch1 or ch2
     if changed:
         try:
             p.write_text(json.dumps(asdict(s), indent=2), encoding="utf-8")
@@ -113,6 +172,7 @@ def load_settings() -> Settings:
 
 
 def save_settings(s: Settings) -> None:
+    s, _ = sanitize_settings(s)
     s, _ = normalize_listen_host(s)
     p = app_data_dir() / "settings.json"
     p.write_text(json.dumps(asdict(s), indent=2), encoding="utf-8")
diff --git a/proxy_chain_manager/gost_util.py b/proxy_chain_manager/gost_util.py
index 4a3cea3..ec007ce 100644
--- a/proxy_chain_manager/gost_util.py
+++ b/proxy_chain_manager/gost_util.py
@@ -22,9 +22,13 @@ GOST_RELEASE_ZIP = (
 def _add_defender_exclusion(path: Path) -> None:
     """Add Windows Defender exclusion so GOST is not quarantined."""
     try:
+        # ExclusionPath covers gost.exe under this folder; avoid invalid combined params on older builds.
+        folder = str(path.parent).replace("'", "''")
         subprocess.run(
-            ["powershell", "-NoProfile", "-NonInteractive", "-Command",
-             f"Add-MpPreference -ExclusionPath '{path.parent}' -ExclusionProcess 'gost.exe' -ErrorAction SilentlyContinue"],
+            [
+                "powershell", "-NoProfile", "-NonInteractive", "-Command",
+                f"Add-MpPreference -ExclusionPath '{folder}' -ErrorAction SilentlyContinue",
+            ],
             capture_output=True,
             timeout=30,
             creationflags=getattr(subprocess, "CREATE_NO_WINDOW", 0),
diff --git a/proxy_chain_manager/service.py b/proxy_chain_manager/service.py
index 93f64e9..70c7cb0 100644
--- a/proxy_chain_manager/service.py
+++ b/proxy_chain_manager/service.py
@@ -375,7 +375,7 @@ class ChainService:
     async def _build_pool(self) -> list[str]:
         """Fetch and validate proxies. Runs blocking I/O in thread pool."""
         s = self._settings
-        loop = asyncio.get_event_loop()
+        loop = asyncio.get_running_loop()
 
         # Fetch all sources concurrently in thread pool (they are blocking)
         async def _fetch_one(url: str) -> list[str]: