Fix APNG info after seeking backwards more than twice

Tests/test_file_apng.py

@@ -689,3 +689,12 @@ def test_different_modes_in_later_frames(mode, default_image, duplicate, tmp_pat
     )
     with Image.open(test_file) as reloaded:
         assert reloaded.mode == mode
+
+
+def test_apng_repeated_seeks_give_correct_info() -> None:
+    with Image.open("Tests/images/apng/repeated_seeks_give_correct_info.png") as im:
+        for i in range(3):
+            im.seek(0)
+            assert im.info["duration"] == 4000
+            im.seek(1)
+            assert im.info["duration"] == 1000

src/PIL/PngImagePlugin.py

@@ -378,7 +378,7 @@ def save_rewind(self):
         }
 
     def rewind(self):
-        self.im_info = self.rewind_state["info"]
+        self.im_info = self.rewind_state["info"].copy()
         self.im_tile = self.rewind_state["tile"]
         self._seq_num = self.rewind_state["seq_num"]