Currently, I'm using the following patch to try to detect bpo-33803 bug using my GC object debugger. It's still a work-in-progress.

diff --git a/Lib/site.py b/Lib/site.py
index ad1146332b..e184080b19 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -638,3 +638,8 @@ def _script():

 if __name__ == '__main__':
     _script()
+
+if 'dev' in sys._xoptions:
+    import gc
+    gc.enable_object_debugger(100)
+    #gc.set_threshold(5)
diff --git a/Python/hamt.c b/Python/hamt.c
index 67af04c437..67da8ec22c 100644
--- a/Python/hamt.c
+++ b/Python/hamt.c
@@ -2478,8 +2478,10 @@ hamt_alloc(void)
     if (o == NULL) {
         return NULL;
     }
+#if 0
     o->h_count = 0;
     o->h_root = NULL;
+#endif
     o->h_weakreflist = NULL;
     PyObject_GC_Track(o);
     return o;