Running a quick search, testdisk finds all of the 3 partitions (NTFS for Windows, Ext4 for Peppermint, and NTFS for data), their sizes are correct (50GB, 420GB, and 30GB, respectively), but under no circumstances I can get rid of the "Structure: Bad" message.

If I select the Windows and Linux partitions, structure is good, if I select the Windows and the "Storage" partitions,
its all good, but whatever I do, I can't select the Linux and Storage and make it work...
Am I clearly stupid, blind, or do I really have a problem here?