Here is a mistake that only reveals itself on the day of delivery: a shelf that will not go in.
The inside of a glazed bay is wider than the door opening in front of it, because the door has stiles down each side and the carcass has posts. Make a shelf to the full internal width - which is the obvious thing to do, since that is the space it has to fill - and it is now wider than the hole it has to pass through. It cannot be angled in either, because it is a rigid sheet of glass and the opening is only so tall.
The rule our master Indian artisans work to is simple: every shelf is dimensioned so that it can pass, on the diagonal, through the largest opening it will live behind. That number is worked out before the shelf is cut, not after the cabinet is glued up.
The consequence is that a shelf in a multi-bay cabinet is very slightly narrower than the bay, and the small gap is taken up by the shelf supports.
It sounds trivial. It is the difference between a cabinet you can restock, re-shelf and clean for forty years, and one where a broken shelf means dismantling a door.