Here is the list discussed in Episode 28 on Burndown Patterns:
Add Things/Remove Things
Not enough refined in the Backlog
Change in priority from stakeholders
Unforeseen events
Ill-defined specifications
Third-party dependencies
Committing to something that’s known to be blocked
Estimations off in either direction
Not enough time spent in planning to know technical details
No acceptance criteria
No Definition of Ready or Definition of Done for the item
Don’t Finish Everything/Finish too early
Not watching Work in Progress – started too many things
Work not accounted for in sprint planning
Bad or no capacity planning
Chronically under/overcommit – fear culture
Other relevant teams not included in sprint planning
Last Minute Fire Drill For Team
Other relevant teams not viewed as team members
Other teams (e.g. DevOps) not considered
Environment failures
Poor strategic planning
Scrum Master not protecting the team
Product Owner not empowered
Sprint is waterfall