diff --git a/harbor/reverse.py b/harbor/reverse.py
index 3cbacbe..a5a7de5 100644
--- a/harbor/reverse.py
+++ b/harbor/reverse.py
@@ -648,6 +648,30 @@ def behaviour_check(config, targets, decomp=None, precision=24):
     return [{k: r[k] for k in keep if k in r} for r in rows]
 
 
+def pid_alive(pid):
+    """True while process `pid` runs (Windows: OpenProcess and GetExitCodeProcess; never signals it)."""
+    try:
+        pid = int(pid)
+    except (TypeError, ValueError):
+        return False
+    if os.name != "nt":
+        try:
+            os.kill(pid, 0)
+            return True
+        except OSError:
+            return False
+    import ctypes
+    kernel = ctypes.windll.kernel32
+    handle = kernel.OpenProcess(0x1000, False, pid)        # PROCESS_QUERY_LIMITED_INFORMATION
+    if not handle:
+        return False
+    try:
+        code = ctypes.c_ulong()
+        return bool(kernel.GetExitCodeProcess(handle, ctypes.byref(code))) and code.value == 259   # STILL_ACTIVE
+    finally:
+        kernel.CloseHandle(handle)
+
+
 class _exclusive:
     """A lock file shared between processes: wait for it, hold it, remove it (stale after two hours)."""
 
@@ -665,7 +689,9 @@ class _exclusive:
                 return self
             except FileExistsError:
                 try:
-                    if time.time() - self.path.stat().st_mtime > 7200:
+                    holder = self.path.read_text(encoding="utf-8").strip()
+                    age = time.time() - self.path.stat().st_mtime
+                    if (holder and not pid_alive(holder)) or (not holder and age > 5) or age > 7200:
                         self.path.unlink()
                         continue
                 except FileNotFoundError: