If you go to AppData\LocalLow\Three Eyes Software\Silverpine\SaveSlots.json, and then delete the "Corrupted Save" part from the slot's description field, e.g.:
"description": "Corrupted Save\nSlot 2 etc.
to
"description": "Slot 2 etc.
It should still be loadable, since in this case it's just flagged as "don't load this", rather than actually be broken.
Also, it turns out this problem can be fixed by simply waiting for 24 hours in the game after loading the 1.3.2 save.
Deleting the Corrupted flag did allow me to load it. After sleeping it did drop the error again:
System.NullReferenceException: Object reference not set to an instance of an object.
at TypeSerializationUtility.SerializeWithType (ISerializable serializable, System.IO.BinaryWriter binaryWriter) [0x00000] in <00000000000000000000000000000000>:0
at RoutineArgument_SeekPlayerAndTalk.Serialize (System.IO.BinaryWriter binaryWriter) [0x00000] in <00000000000000000000000000000000>:0
at TypeSerializationUtility.SerializeListWithType[T] (System.Collections.Generic.List`1[T] list, System.IO.BinaryWriter binaryWriter) [0x00000] in <00000000000000000000000000000000>:0
at NPCRoutine.Serialize (System.IO.BinaryWriter binaryWriter) [0x00000] in <00000000000000000000000000000000>:0
at WalkUpManager.Serialize (System.IO.BinaryWriter binaryWriter) [0x00000] in <00000000000000000000000000000000>:0
at SerializationManager.SerializePersistent () [0x00000] in <00000000000000000000000000000000>:0
at SerializationManager.Save (System.String saveFileName) [0x00000] in <00000000000000000000000000000000>:0
at SaveUI.Save (System.Int32 saveSlot) [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.Events.UnityEvent.Invoke () [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.StandaloneInputModule.ReleaseMouse (UnityEngine.EventSystems.PointerEventData pointerEvent, UnityEngine.GameObject currentOverGo) [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.StandaloneInputModule.ProcessMousePress (UnityEngine.EventSystems.PointerInputModule+MouseButtonEventData data) [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.StandaloneInputModule.ProcessMouseEvent (System.Int32 id) [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.StandaloneInputModule.Process () [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.EventSystems.EventSystem.Update () [0x00000] in <00000000000000000000000000000000>:0
After waiting 24 ingame hours it did fiy itself. Thank you!
