Symptoms
After a migration involving a content type with a document information panel, you get one of the following warnings:
The content type '<CONTENT_TYPE>' contains a custom document information panel which is not supported by ShareGate Migrate.
Custom document information panel on content types are not supported by ShareGate Migrate.
Details
As of Office 2016, the Document Information Panel content type is no longer supported. Managed Metadata columns are also not supported in the Document Information Panel, and have been replaced by Document Properties.
There is no workaround to this issue.