Compatibility between 2016.1.5999 and 2018.1.4

Do you know differences in 2016.1.5999 and 2018.1.4?
When I made some click activities with 2016.1.5999 and worked with 2018.1.4 ,
Some click activities didn’t move and showed errores below.
I took capture with 2018.1.4 again using Indicate on Screen,and they workded.

But wordings in Selectors were the same, Do you know the phenomenon?

・Error Message

System.NullReferenceException: Object reference not set to an instance of an object.
at System.Activities.ExpressionUtilities.ArrayLocationFactory1.ArrayLocation.set_Value(T value) at System.Activities.Location1.ReferenceLocation.set_Value(T value)
at System.Activities.Location`1.set_ValueCore(Object value)
at System.Activities.ActivityContext.SetValueCore[T](LocationReference locationReference, T value)
at System.Activities.ActivityContext.SetValue[T](LocationReference locationReference, T value)
at System.Activities.Argument.Set(ActivityContext context, Object value)
at System.Activities.Statements.Assign.Execute(CodeActivityContext context)
at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
at System.Activities.ActivityInstance.Execute(ActivityExecutor executor, BookmarkManager bookmarkManager)
at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)