When doing a pre-migration check or copying a site object, the following message is displayed:

The term set this column refers to cannot be found in the source site.The column seems to be corrupted.
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Error code

The message is displayed when the term set used by a source column is missing at the source.

Here is an example for a column named "Project" that is driven by a term set "Projects". Here is the term set:

In this example, the error would mean that the term set "Projects" cannot be found at the destination.

When this happens, it means that the source column is corrupted and so it does not contain any useful data any more. As a result, the column can often be deleted without losing any important data.

Another way to resolve the issue would be to update the column's settings to refer to an existing term set. This can be done by going in List Settings and clicking on the column, then choosing a term set in the Term Set Settings section.