Quick update: I spoke to the Grundbuchamt and the guy there was very friendly and helpful. Due to timing, I only had 30 minutes with him so might need to make a separate appointment to discuss in more detail.

An initial review flagged no special issues, but I will need to ask about the Quartier/Gemeinschaft point raised earlier. Hopefully this is also lodged with the Grundbuchamt.

Just as I thought the whole process could not get more stressful, the agent said that they might not get all the paperwork done in time before the movers are scheduled.

And if that wasn't enough, the company I work for has been taken over. interesting times ahead...