Comment by stevage

Two problems:

- they started to realise they didn't have some of the domain knowledge (I specialise in maps/GIS), so couldn't steer it effectively

- they said that the changes it made started to become unstable: while making one change, it would break other things. It got harder and harder to make progress.

I suspect the second problem wouldn't happen as soon (or maybe not at all) with an experienced dev running the process.