Additional cost due to oversight made by city and possibly architect. Who pays?

[Chris Morris]

I am working with a great architect on my first new development project (who I found on Bigger Pockets). We met with the city twice for 'preliminary plan check' and are now going through the formal plan check process. During the formal plan check process, the city noticed that we were not interpreting the encroachment plane properly, which means we had to redesign the attic. This required changes to the structural engineering, which the structural engineer is charging me for. Who should pay for these changes: the architect or me? All parties involved missed this mistake (the city during preliminary plan check, the architect, and myself). The architect pointed out that I should pay, given that we screened our design twice with the city during the preliminary plan checks. I get that perspective. However, I also see the perspective that the architect is expected to know about the main setback/encroachment requirements, with the encroachment plane being one of those requirements.

Is it reasonable for me to pay 100% of the charges? Should we split them? Or something else?

If this matters, my current contract w/ the architect is a fixed price for them to get the project through plan check.

Also, it is likely that my architect sees this post (I found them on Bigger Pockets). In this case, please know that no offense is meant. I am trying to be thorough with my due diligence, especially since this is my first project and I am hoping to build up my knowledge base and set myself up for success for future ground-up development projects with you. :-)