All of the above I would say can turn a good situation into bad. But most of the time I have found myself somewhere in between #1 and #2. And I have never come across a silver bullet or a single factor that caused the #2. Just keep on changing and reflect wether the suggested change could lead to a more agile/lean outcome. Validate vs the 12 principles or the Scrum values and guide and of course your own agile instinct. But you will only know at the next inspect and adept opportunity. So retro often, make it targeted and do this throughout the organisation. Surround yourself with people who like this process and you are more likely to succeed.