Some folders are too long even when shrunk.
This error occurs when the Advanced Option ShrinkFoldersMaxLength is set but the folder structure at the Source is so long that it cannot be shrunk enough to fit the requirement. This usually happens when there is a large number of nested folders.
The number of nested folders at the Source will have to be reduced to allow the shrinking algorithm to find a combination that fits the requirement. Moving some deep folders up the folder tree will usually help with this issue.