Answer
Check whether the Migration Job ID itself contains a space or a hyphen — the Excel migration add-in uses the job ID to dynamically generate procedure names internally, and a space or hyphen in that ID breaks that dynamic procedure creation, producing this exact savepoint error. Stick to letters, numbers, and underscores only in Migration Job IDs going forward. For a migration job that's already been created with a problematic ID, right-click it and choose 'Copy Migration Job' to create a working copy under a new, valid name, rather than trying to rename the existing broken one directly.