We can run it, but reporting and controls still trip us up

You can run the function. That part works. Then a report pulls numbers you did not expect, or a control does something nobody asked it to do, and suddenly the whole thing feels foreign again. This is not a skill problem. You already have the skill — you proved it when you ran the function. What you have is a system you have not actually examined, and you are trying to hold all of it in your head at once. No one can debug a whole system in their head. Not you, not your team, not anyone. Working with others makes this worse if you let it. One person's confusion blurs into another's, until the whole team agrees 'it's all confusing' and stops there. Pull it apart. Find the exact line where each person's understanding breaks, and work that line alone.