It turned out, after long research, that the Quickport does not support disks larger than 2TB. But it didn't show any problem, I guess until I reached the 2TB threshold when writing.
Anyway, I run testdisk last night. Before start it told me it didn't find any partition. This is what I found in the morning:

Can you recommend what to do? There's a lot of data on these hard drives. On both the same, I took the precaution of having that data on 2 hard drives, but now both are unreadable...