To be so fair it hurts, they do have a huge problem there. Working on pipes by robot sub at that depth has been compared to doing heart surgery in the dark with tongs; as for dropping the dome on it, I'd compare that to putting an extinguisher on a candle by lowering it from the roof of an apartment block on a string.
But this is exactly why they should have had backups on their backups, so the insoluble problem didn't happen. A famous manual of sailing offered the advice on what to do when caught on a lee shore on a falling tide: "Never get into this situation."