I have the same issue, but it’s not with all widgets. I could install from the UI the Battery Level Status and Universal Toggle ; however, I couldn’t install the Washing machine status widget or Dishwasher Status.
Most probably what @rlkoshak mentioned is correct, although these are not new widgets. They seem to have been published and downloaded by many people since February.
Edit: I only get this error, not the one with the YAML: