UI Upgrade from SharePoint 2010 to 2013

Hello,

I've a huge sharePoint content database. This Content database was migrated to SharePoint 2010 approx. 2 years ago.
Now I'm trying to migrate this database to SharePoint 2013.

I executed Test-SPContentDatabase, Mount-SPContentDatabase and the database attached successfully to the new SharePoint 2013 farm. All the migrated content is available and all custom Features are working as expected.

But the UI-Upgrade process is producing over 9.000 Errors. A lot of them are:

Feature upgrade incomplete for Feature 'Publishing' (Id: 15/'22a9ef51-737b-4ff2-9346-694633fe4416') in Web
'http://xxxxx'. Exception: Invalid field name.
{8484dbaf-e6d2-4f98-9aa7-e19f89260224}  /Variation Labels 61fba69c-193a-30bd-b0b4-77dd0e8b1166
07/22/2014 14:55:57.01 OWSTIMER (0x1558) 0x1940 SharePoint Foundation Upgrade SPFeatureDefinition

Feature upgrade action 'CustomUpgradeAction.EnsureVariationsInfrastructure' threw an exception upgrading Feature 'Publishing'
(Id: 15/'22a9ef51-737b-4ff2-9346-694633fe4416') in Web 'http://xxx':
Invalid field name. {8484dbaf-e6d2-4f98-9aa7-e19f89260224}  /Variation Labels 61fba69c-193a-30bd-b0b4-77dd0e8b1166

Feature upgrade action 'CustomUpgradeAction.EnsureVariationsInfrastructure' threw an exception upgrading Feature 'Publishing'
(Id: 15/'22a9ef51-737b-4ff2-9346-694633fe4416')
in Web 'http://xxxx': Invalid field name. {8484dbaf-e6d2-4f98-9aa7-e19f89260224}  /Variation Labels 61fba69c-193a-30bd-b0b4-77dd0e8b1166

All necessary language packs are installed.

I tried this without success:

http://social.technet.microsoft.com/Forums/de-DE/00bf12f7-730d-4ff6-a973-ce1bf92d4691/error-while-upgrading-2010-mode-site-collection-in-2013-to-2013-mode-site-collection?forum=sharepointadmin

Maybe someone has some tips for me?

-