GGB The recurring causes are almost never exotic: incomplete submissions that trigger resubmission loops with the authorities; a unit whose handover condition turned out to be rougher than the lease implied; design revisions made after approval that restart review clocks; long-lead kitchen equipment ordered late; hiring started after the build instead of alongside it, so visas and training miss the finished premises; and work run in sequence that could have run in parallel while the rent clock ran regardless. Nearly every delay is a governor that was ignored rather than managed.
From The Restaurant Opening Timeline — What Actually Governs It — the full reading, with the method behind this answer.