ReplaySubject<string[]> rep = new ReplaySubject<string[]>(1);
rep.OnNext(new[] { "start" });
rep
  .Take(1)
  .Subscribe(strings => {
    var list = strings.ToList();
    list.Add("added");
    rep.OnNext(list.ToArray());
  });

InvalidOperationException: Collection was modified after the enumerator was instantiated.
System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) (at <3649452ae23840d49bd323a708498f78>:0)
System.Collections.Generic.Queue`1+Enumerator[T].MoveNext () (at <3649452ae23840d49bd323a708498f78>:0)
UniRx.ReplaySubject`1[T].Subscribe (System.IObserver`1[T] observer) (at Assets/Plugins/UniRx/Scripts/Subjects/ReplaySubject.cs:170)
UniRx.Operators.TakeObservable`1[T].SubscribeCore (System.IObserver`1[T] observer, System.IDisposable cancel) (at Assets/Plugins/UniRx/Scripts/Operators/Take.cs:58)
UniRx.Operators.OperatorObservableBase`1[T].Subscribe (System.IObserver`1[T] observer) (at Assets/Plugins/UniRx/Scripts/Operators/OperatorObservableBase.cs:34)
UniRx.ObservableExtensions.Subscribe[T] (System.IObservable`1[T] source, System.Action`1[T] onNext) (at Assets/Plugins/UniRx/Scripts/Observer.cs:413)