Therefore we have installed a fresh copy of Xenforo and Media Gallery. After this used the admin option to import the database and images from Xenforo 1.2+. We did this to ensure that ONLY the expected data was imported.
Our major problem is that our Media Gallery with thousands of user contributed images wasn't imported. There is no option in admin to import anything from Media Gallery. So how can we import the Media Gallery and make sure it only copies the expected files? We neither trust the database nor the 'data' and 'internal_data' folders... so just copying these to the freshly installed forum is not an option.
Many thanks in advance for any help!