Every drawing set is a web. A plan points to a section, the section points to a detail, the detail points to a specification. Pull one thread and something at the other end moves.
Across the sets we reviewed this year, about one finding in five was a reference to a detail, a section or a sheet that had been renumbered or deleted. Not a design error, just a pointer to nowhere.
Why it keeps happening
Details get renumbered when a sheet fills up. Sections get deleted when the design changes. Nobody goes back through every sheet to find the callouts that pointed at them, because nobody has the time.
On site, a broken reference turns into a phone call, then an RFI, then a delay. The fix on paper takes a minute; the fix on site takes a week.
What helps
Check references on every issue, not only before tender. Keep a register of renumbered details. And when a detail is deleted, search the whole set for its number before the set goes out.