Symptoms
Sharegate displays the following error:
The item '<item name>' already exists at the destination site. Items can only be updated with Insane Mode if they were initially created by the Insane Mode as well.
Error code
AZ-020-215
Any error code ending with: -215
Details
This error occurs because the item already exists at the destination site and was previously migrated using the normal mode of Sharegate. Items can only be updated with Insane Mode if they were initially created by the Insane Mode as well.
The reason behind this limitation is that when copying an item in Sharegate using the Normal Mode, the Unique Identifier of the item is not preserved and a new Unique Identifier is given to the copied item at destination. However, when using the Insane Mode to make the copy, we are using another API provided by Microsoft which preserves the item Unique Identifier when copying it at destination. Therefore, if the item already exists at destination with a different Unique Identifier, Sharegate receives an error from the Microsoft API which results in a failed copy of the item.
Solution
Note: You must be Site Collection Administrator for this solution.
Delete the item from your destination list.
At your destination site, delete your item from your first-stage recycle bin either by clicking Recycle Bin in your navigation pane or by going into your Site Collection Settings and clicking Recycle Bin under the Site Collection Administration section.
Delete your item from your second-stage recycle bin by clicking the "second-stage recycle bin" link in your first stage recycle bin page.
Start again your copy using the Insane mode.
Or
Use the Normal Mode to copy the item in the destination list.