Migrations rarely fail on the data. They fail on the URLs nobody mapped, the schema nobody noticed
The single largest migration risk is URLs, and it is entirely preventable with a complete redirect map.
Do not migrate and redesign simultaneously — when traffic moves, you will not know which change caused it.
Structured data, heading hierarchy and internal links are lost quietly, because nothing visibly breaks when they go.
Expect a settling period of weeks to months, and agree in advance what would count as a problem.
It can, and the causes are predictable rather than inherent.
The full guide has the formats, the deadlines and the worked examples.