Workaround:
To force items to migrate using Azure, go to %appdata%\Metalogix\Content Matrix Console - SharePoint Edition, look for ApplicationSettings.xml, open the file and change the value of the following key:
<Key>ListNamesToIncludeForAzure</Key>
<Value>LibraryName</Value>
NOTE: You have the option of overriding the default behavior so that if a library contains both supported and unsupported objects, the entire library will migrate using CSOM. To do this, change the value of the key AllowPartialPipelineMigration in the configuration variable file EnvironmentSettings.xml from true to false.