I encountered issues with imported images in frontend and backend, the meta data of the files couldn't be found resulting in an exception:
#1314226805 InvalidArgumentException: Property "width" was not found in file reference or original file.

sys_file_metadata records were imported to the target pid instead of the root level, issue exists in 11.3 and 12.8.

I'm not quite sure if I've missed something, but I think a check for the TCA rootLevel setting in In2code\Migration\Port\Import->prepareProperties() should solve this issue.