The community member is facing an issue with a "SubQuestionQueryEngine" and is receiving a "KeyError: 'node_id of the fetched node'" error. The comments suggest that this is likely a key error, and the community members are unsure about the query engine tools being used. One community member suggests setting use_async=False to get a better traceback, but this does not seem to have resolved the issue. The community members are asking for more information about the query engine tools and the kind of index being used, and they suggest that providing some code would help with debugging the issue.
