Avoidable project manager's mistakes screw up projects

Of all the reasons the projects can fail, wrong estimation would likely be the first. By nature, estimations are expected to be prone to some variations and its a project managers responsibility to make it as close to reality as possible. More importantly, a project manager has to be communicate the risks, assumptions, dependencies and any other issues with the estimations and the resulting impact on projects.

Even if it sounds so easy, i find it often that not all the risky and assumptions get communicated. Many times, there is pressure from some decision makers to make the project manager own the risks by ridiculing or by other funny tactics. Its important for a PM to be strong enough to back up his statement inspite of political pressures and highlight the issues and take corrective actions.

Some of the repetitive mistakes, project managers in different companies have been observed to make:
1. RAID matrix doesn't get published and revisited periodically.
2. Initial estimations never get challenged if required. Accept the risk if the by default strategy by some unwritten rules in most companies (honestly scrum teams score better in this aspect)
3. Weaker PMs often say it quits when faced with tricky situation. This impacts the team more than anything else. I agree that project management is more political than most other disciplines however the PM still has to be skillful enough to put his point across and get the community moving.
4. Absence of variance from original estimates is hardly backed up in most organizations.
5. If the projects are run by multiple organization entities, I find it sometimes stranger that participating PMs even end up screwing the program success parameters in their effort to keep their territory cleaner.