I'm not sure why the file path isn't correctly being passed to the connector. It may have to do with File System - Connectors - General Limits | Microsoft Learn where a maximum file size 30MB is being met. If you're setting File to an upstream output, does it inspect correctly?
As a workaround, I suggest using File System - Connectors - List files in root folder | Microsoft Learn to get the contents of root and iterate through the array result.