So I have that ship that splits into 3, once it is split the above happens.
This is what I found in the logs:
[EXC 21:55:05.272] NullReferenceException: Object reference not set to an instance of an object
KSP.Sim.impl.VesselComponent.GetState () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Serialization.SerializationUtility.VesselToSerializable (KSP.Sim.impl.SimulationObjectModel vessel, System.Boolean isAutosave) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Load.CollectFlightDataFlowAction.CollectVesselComponents (System.Byte playerID) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Load.CollectFlightDataFlowAction.DoAction (System.Action resolve, System.Action`1[T] reject) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Flow.FlowAction.Do (System.Action`1[T] resolve, System.Action`2[T1,T2] reject) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Flow.SequentialFlow.NextFlowAction () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.Flow.SequentialFlow.StartFlow () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadManager.PrivateSaveCommon (KSP.Game.LoadOrSaveCampaignTicket loadOrSaveCampaignTicket, KSP.Game.Flow.SequentialFlow savingFlow) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadManager.PrivateSaveGameToFile (KSP.Game.LoadOrSaveCampaignTicket loadOrSaveCampaignTicket) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadManager.StartLoadOrSaveOperation (KSP.Game.LoadOrSaveCampaignTicket loadOrSaveCampaignTicket) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.LoadOrSaveCampaignTicket.StartLoadOrSaveOperation () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadManager.SaveGameToFile (System.String filepath, KSP.Sim.SavedGameType savedGameType, System.Boolean saveOverwriteFileIfExists, KSP.Game.OnLoadOrSaveCampaignFinishedCallback onLoadOrSaveCampaignFinishedCallback) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadDialog.SaveFile () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Game.SaveLoadDialog.OnNewSaveFile () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Delegate.DynamicInvokeImpl (System.Object[] args) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Delegate.DynamicInvoke (System.Object[] args) (at <695d1cc93cca45069c528c15c9fdd749>:0)
KSP.Api.CoreTypes.DelegateAction.InternalInvoke (System.Boolean catchExceptions, System.Boolean fillArgsWithoutDefault, System.Object[] args) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
KSP.Api.CoreTypes.DelegateAction.Invoke (System.Object[] args) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
UIAction_Void_Button.OnButtonLeftDown () (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
UnityEngine.Events.InvokableCall.Invoke () (at <25a85da7c6f04932b86e339dfd12957d>:0)
UnityEngine.Events.UnityEvent.Invoke () (at <25a85da7c6f04932b86e339dfd12957d>:0)
UnityEngine.UI.ButtonExtended.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at <8c5bdf369a8c45f68951f69eb825ef73>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at <6026956e4abc48a7aa322d4d816d9190>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at <6026956e4abc48a7aa322d4d816d9190>:0)
UnityEngine.EventSystems.ExecuteEvents:Execute(GameObject, BaseEventData, EventFunction`1)
ModifiedInputModule:ProcessMousePress(MouseButtonEventData, MouseButton)
ModifiedInputModule:ProcessMouseEvent(Int32)
ModifiedInputModule:ProcessMouseEvent()
ModifiedInputModule:Process()
UnityEngine.EventSystems.EventSystem:Update()
Then I can not load or save until I quit the game.
Also, it seems no action is set to the destroy debris button.