Reading a few different articles about this today.
Boy…sounds like Lord and Miller really fucked around with this. Jesus. From what I read, Ron Howard basically used the production design, a few action scenes, and that’s about it. He was basically asked to re-shoot the whole movie in half the time and due to Lord and Miller wasting so much time and having nothing to show for it it has cost Disney almost twice the expected budget. Sounds like Lord and Miller were treating it as their personal play ground and toy box and were not very professional in terms of shooting schedule and communicating with Kennedy and Kazdan.
The flip side is Disney is very happy with what Ron Howard was able to do in such a short time and will not allow the mistakes of Lord and Miller disrupt plans for future spin offs.