You try to migrate an item, and you get the following error:

There are multiple destination items that correspond to the given key values for the lookup item '1'. The first one was assigned, but it might not be the one that was expected.

The error occurs when the given field points to an ID column and ShareGate Migrate finds multiple corresponding items at the destination.

Since ShareGate Migrate does not always preserve IDs at the destination, ShareGate Migrate must map the source item to a destination item based on the Title and Created fields.

While these properties are enough to ensure only one match at the destination, they may not be sufficient in some cases.

To ensure a proper match for your lookup column, you need items in the looked-up list with unique values in either the Title or Created field.

You can use Bulk edit content to modify these values with Excel at the source. For example, you can increment the values in the Created column by 1 second.