is "Data Migration Strategy" document part of your project deliverables?
During my experience of managing large and small ERP Implementation projects, either On-prem or Cloud, the biggest delays are caused by Data Migration.
Specially if your project scope involves transformation of your Organization structure. Make sure you allocate a significant amount of time and resources for this activity. This may sound simple but in reality could be the biggest reason for delays to your Go-Live date.
Scope creep (aka Kitchen Sink Syndrome) in Project Management refers to changes, continuous or uncontrolled growth in a project's scope, at any point after the project begins. This can occur when the scope of a project is not properly defined, documented or controlled.