“Object Reference not set to an instance of an object” means your varaible isn’t initialized or doesn’t exist. Without being able to see the full expression my guess is you don’t have an OutputFilePath in in_Config.
Actually now that I think about it, if you didn’t have an OutputFileName in in_Config it probably would give you a “key doesn’t exist” error. You probably don’t have in_Config passed properly. Are you just running CopyingInputFilesToLocalFolder.xaml? You can’t do that if it has input arguments. There won’t be a value for those arguments.
I actually did. It was an internal bug, the activity was corrupted because of some unknown reason that I wasn’t able to figure out, but recreating it did the trick. Happened to me a few times. Can’t recall which Studio version I was using (probably 20.*)