There have been a few times where we would commit to the problem, assign a DRI, and then find out midway that... no we have to hire/consult our way out of the issue. I think that's okay, we then look back at the retro to see what we missed.
If interested, I think we can blog about what happens when a problem gets converted to an RFC and then we have more engineering discussions with the stakeholders but the piece was pushing a 10 min read time as it was...