They've given out vague explanations such as a software glitch, while holding the detailed post-mortem back claiming the obviously absurd excuse of national security concerns.
This is counter to how they typically operate as well as how most other agencies/companies around the world operate these days, where they at least explain what went wrong. eg Hakuto-R's team explaining that their flight software thought the radar altimeter was malfunctioning when it wasn't, causing it to rely on the IMU and thus it thought the surface was much higher than it actually was.
Might want to update your general knowledge. The ISRO Chief explained this in an interview. It wasn't just passed off as "software glitch" with no explanation.
Chairman S Somanath has given three main reasons that led to the crash-landing of the Vikram lander on September 6, 2019 just minutes before the touchdown.
The ISRO chairman said, “The primary issues were: One, we had five engines which were used to reduce the velocity (called retardation). These engines developed higher thrust. When such a higher thrust was happening, the errors on account of this differential were accumulated over some period. All the errors accumulated, which was slightly higher than what we expected.
When it (lander) started to turn very fast, its ability to turn was limited by the software because we never expected such high rates to come. This was the second issue.
The third reason for failure was the small site of 500m x 500m for landing of the lander.”
Rectifying those mistakes this time, the Isro chairman said, “This time we have kept an area of 4.2 km (along the track) x 2.5 km (width) for the landing site. So, it can land anywhere, so it doesn’t limit you to target a specific point.”
Somanath said “instead of a success-based design, Isro has this time opted for a failure-based design” and focused on what all can fail and how to protect it and ensure a successful landing.
“We looked at sensor failure, engine failure, algorithm failure, calculation failure. So, there are different failure scenarios calculated and programmed inside. We did new test beds for simulation, which was not there last time. This was to look at various failure scenarios,” he explained.
The ISRO chief said the Vikram now has additional solar panels on other surfaces to ensure that it generates power no matter how it lands.
What do you mean by "they haven't officially straight-up announced the issue." ? They did so - several times actually.