When evaluating this kind of conspiracy theory, it's important to consider the number of people who would have to remain silent for the conspiracy to survive, and to consider how much it would cost to keep that many people silent. In this case, it's at least a few dozen so I think it's fair to assume that such a lie would not survive very long.
As far as examples of successfully kept secrets, I can’t give those, because I’m in on it.
All a conspiracy is, is a group of people keeping a secret.
As far as conspiracies not being successful long term, history tells us no such thing. Conspiracies with tons of people are successfully kept every single day, only to be discovered decades later when something is declassified for example.
You can never prove if a conspiracy to keep a secret is not successful if you never knew it existed.
Am I making any sense?
I’ve seen estimates as high as 10% of the population of east Germany were spying on their neighbors.
Naming conspiracies that have never leaked is kind of hard, since we wouldn't know about them. So you have to look for examples of things that were talked about after they stopped being relevant, or that were uncovered without anyone blabbing.
You sound paranoid.
This is a very unlikely expectation. Employees are under NDA so nobody will talk publically about it unless one of them feel so strongly about it to sacrifice their career (they'd certainly get fired, and being sued for breaching the NDA isn't going to make finding a new job easier).
Employees at all companies keep quiet about bugs like these all the time, that's the most common outcome.
NDAs are unenforceable against whistleblowers who report illegal activity.
Replace "eventually" with "maybe".