Ok, I found what is happening. If you only have output pins you can ignore this error for now, setting will still work I think.
What happens is that the reading can fail and goes to error state. Now you can only see an error when we do not delete it, so it stays forever or until you save and resets all error states. This specific error happens when reading pin state does not return 0 or 1 so probably when linux is just updating it's value. So more a temporary error and I will remove the error in that case in future release.
