Another member objected when I posted recently that the DPI evidence fits like a glove. I think the problem is that many people let the details, which may never be entirely understood, distract them from the obvious "big picture." This may be the major obstacle to most people who want to be professional investigators of one type or another. They seem to want a standard of "beyond all doubt" rather than beyond reasonable doubt, and the standard is even lower for civil cases (in the USA). In some nations there is an official inquest, where they decide what was the most likely scenario, though that may not result even in an indictment, though the inquest determined it was likely a homicide, for example. In some homicide cases, there is only one person who could have been responsible for it, though there is no evidence because that one person apparently cleaned up the crime scene; this scenario is a bit like the DPI, because with the DPI there is only evidence for one possible explanation of the "big picture." However, so many people will get caught up on details, some of which may require repeated reconstructions done by experts.
A couple of other cases that demonstrate either a basic investigative failure or a "failure of imagination:" a young girl died in a circus tent fire in 1944 but was not identified for decades, despite the fact that her face was easily identifiable. Eventually DNA testing solved the case, the problem apparently was that the parents were shown the wrong body and said, of course, that it wasn't their daughter. The only explanation is that the authorities were overworked, due to how many deaths there were during this incident. Another case involved a woman who was thought to have died as a result of jumping off the Golden Gate Bridge. However, it was discovered during autopsy that she had a gun shot wound to the head, which must have been the cause of death. Investigation uncovered a witness, who said the woman appeared fine, and just jumped off the bridge (nobody else was present). The woman she lived with said that the victim was saying she would jump off the bridge but shoot herself as she was falling, to avoid being alive for a while and in pain. They would have investigated her for possible homicide charges, as the gun was never found and the story sounded like nonsense, but the witness was adamant, and a suicide note was found in the handwriting of the person who committed suicide.
In the DPI, there is no good reason to question anything other than the judgement of the group (and Zina may have finally had enough and decided to go back to the tent after witnessing the deaths of the two Yuris), though obviously the investigation was not optimal (was it consistent with that nation and time period, though?). And that brings me to a key point that most just seem to ignore: you will never likely get one explanation for everything that happened with the group that night. It's highly unlikely we will ever learn if the idea to dig the "den" was part of an original plan or decided upon (by all or just some of them) at a later time, for example, just like we don't understand the rationale of the Chivrauy group more than a dozen years later. And the Korovina group seems to have been "gripped by madness," perhaps related to lack of food and psychological stress. By all means, keep other possibilities in the back of your mind, and if the evidence comes to light that supports one of those, then investigate further. Until then, I think you'd find your free time better utliized by studying other "mysteries" and cases that puzzled the "experts" for a while before they finally figured out at least the big picture, as to what occurred.