diff --git a/Lib/test/test_interpreters/test_api.py b/Lib/test/test_interpreters/test_api.py
index 01856d9bf67657..9c02efe71683f6 100644
--- a/Lib/test/test_interpreters/test_api.py
+++ b/Lib/test/test_interpreters/test_api.py
@@ -703,6 +703,7 @@ def test_not_shareable(self):
         with self.assertRaises(ExecutionFailed):
             interp.exec('print(spam)')
 
+    @support.skip_if_sanitizer('gh-129824: file descriptor race', thread=True)
     def test_running(self):
         interp = interpreters.create()
         interp.prepare_main({'spam': True})
@@ -1530,6 +1531,7 @@ def test_whence(self):
             whence = eval(text)
             self.assertEqual(whence, _interpreters.WHENCE_LEGACY_CAPI)
 
+    @support.skip_if_sanitizer('gh-129824: file descriptor race', thread=True)
     def test_is_running(self):
         def check(interpid, expected):
             with self.assertRaisesRegex(InterpreterError, 'unrecognized'):
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 154cde9316866e..30dc4685d8a813 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -4231,7 +4231,8 @@ _PyExc_InitTypes(PyInterpreterState *interp)
             return -1;
         }
         if (exc->tp_new == BaseException_new
-            && exc->tp_init == (initproc)BaseException_init)
+            && exc->tp_init == (initproc)BaseException_init
+            && _Py_IsMainInterpreter(interp))
         {
             exc->tp_vectorcall = BaseException_vectorcall;
         }
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index f3238da8a642e4..f94c773a427e85 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -234,10 +234,10 @@ managed_static_type_state_init(PyInterpreterState *interp, PyTypeObject *self,
         ? index
         : index + _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES;
 
-    assert((initial == 1) ==
-            (_PyRuntime.types.managed_static.types[full_index].interp_count == 0));
-    (void)_Py_atomic_add_int64(
+    int64_t prev_interp_count = _Py_atomic_add_int64(
             &_PyRuntime.types.managed_static.types[full_index].interp_count, 1);
+    assert((initial == 1) == (prev_interp_count == 0));
+    (void)prev_interp_count;
 
     if (initial) {
         assert(_PyRuntime.types.managed_static.types[full_index].type == NULL);
@@ -8506,7 +8506,12 @@ type_ready_set_new(PyTypeObject *type, int initial)
         && base == &PyBaseObject_Type
         && !(type->tp_flags & Py_TPFLAGS_HEAPTYPE))
     {
-        type->tp_flags |= Py_TPFLAGS_DISALLOW_INSTANTIATION;
+        if (initial) {
+            type->tp_flags |= Py_TPFLAGS_DISALLOW_INSTANTIATION;
+        }
+        else {
+            assert(_PyType_HasFeature(type, Py_TPFLAGS_DISALLOW_INSTANTIATION));
+        }
     }
 
     if (!(type->tp_flags & Py_TPFLAGS_DISALLOW_INSTANTIATION)) {
@@ -8521,12 +8526,22 @@ type_ready_set_new(PyTypeObject *type, int initial)
         }
         else {
             // tp_new is NULL: inherit tp_new from base
-            type->tp_new = base->tp_new;
+            if (initial) {
+                type->tp_new = base->tp_new;
+            }
+            else {
+                assert(type->tp_new == base->tp_new);
+            }
         }
     }
     else {
         // Py_TPFLAGS_DISALLOW_INSTANTIATION sets tp_new to NULL
-        type->tp_new = NULL;
+        if (initial) {
+            type->tp_new = NULL;
+        }
+        else {
+            assert(type->tp_new == NULL);
+        }
     }
     return 0;
 }
@@ -8659,7 +8674,12 @@ type_ready(PyTypeObject *type, int initial)
     }
 
     /* All done -- set the ready flag */
-    type->tp_flags |= Py_TPFLAGS_READY;
+    if (initial) {
+        type->tp_flags |= Py_TPFLAGS_READY;
+    }
+    else {
+        assert(_PyType_HasFeature(type, Py_TPFLAGS_READY));
+    }
     stop_readying(type);
 
     assert(_PyType_CheckConsistency(type));