Bad story-telling or bad production?

Rating: 7/10 (13 August 2017)

It's an enjoyable film but suffers from either bad story-telling or bad production:
SPOILERS BELOW
From the time David cut his hair, I felt that the filmmakers want to confuse us about the identities of David and Walter at some point. The fluke scene was probably a way for David to learn how Walter behaves.
Fast-forward to the last fight between the two, however, it was obvious that Walter got out, not David: David had a deep puncture wound in his chin, but the one that got out didn't have that wound. At the same time, Walter had a cut to his left cheek, and the one that got out had the exact same cut.
However, couldn't Walter heal himself? --- David can't, so if it was him he should have a wound in his chin, but Walter can and he should be healing over time.
Some viewers may have the theory that David gained control of Walter but was unfamiliar with the software of the newer model. However, I think there is only one plausible explanation that is different:
1. Why was this planet not discovered in the initial scanning? Probably because the company knew what was happening there.
2. Why was there a blast right when they were next to the planet, and when their shields were deployed? Probably because Walter was in on it from the beginning.
3. What was Walter doing by taking out an embryo at the beginning of the film, before the accident? Maybe he was making room for the "new passengers" to be picked up.
Therefore, the whole Walter-David thing is perhaps a red herring: Walter is just a newer David, and his mission was the lead the team to the planet to pick up the old David's research. Walter is every bit of David as David is.
But there is enough bad story-telling so that the viewers can never know --- that is, before seeing the next film.