When attempting to copy an item, Sharegate displays the following message:
The folder 'MyFolder' has a lookup value 'Item1' which refers to one of it's children. The lookup value will be removed.
Any error code ending with: -214
This error occurs when copying a folder with a self lookup column referring to one of its children using Normal mode. The folder must exist to copy the item but the item requires that the folder exist to be copied. When the column is required, the copy will result in an error and the item won't be copied. When the column is not required, a warning will be display and the folder will be copied without the lookup value.
To solve the issues, make sure the column is not required at the destination prior the copy. The folder at the destination will need a manual update to set the lookup value to the child item once the copy is completed to preserve the value.
This is supported when using Insane mode when migrating to Office 365.