Fixed with weakref, needs to be done in other signals too

opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/export/__init__.py

@@ -22,6 +22,7 @@
 from threading import Event, Lock, RLock, Thread
 from time import time_ns
 from typing import IO, Callable, Dict, Iterable, Optional
+import weakref
 
 from typing_extensions import final
 
@@ -490,8 +491,9 @@ def __init__(
             )
             self._daemon_thread.start()
             if hasattr(os, "register_at_fork"):
+                weakself = weakref.proxy(self)
                 os.register_at_fork(
-                    after_in_child=self._at_fork_reinit
+                    after_in_child=lambda: weakself._at_fork_reinit()
                 )  # pylint: disable=protected-access
         elif self._export_interval_millis <= 0:
             raise ValueError(