StashItemsToChest error when >999 items would be in destinat

[18:42:55 ERROR SMAPI] A mod failed handling the GameEvents.UpdateTick event:
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at StashItemsToChest.StashItemsToChest.StashUp(KeyboardState currentKeyboardState)
   at StashItemsToChest.StashItemsToChest.UpdateTickEvent(Object sender, EventArgs e)
   at StardewModdingAPI.Framework.InternalExtensions.SafelyRaisePlainEvent(IMonitor monitor, String name, IEnumerable`1 handlers, Object sender, EventArgs args) in D:\source\_Stardew\SMAPI\src\StardewModdingAPI\Framework\InternalExtensions.cs:line 32