I know I'm a tad paranoid, but I just want to be as careful with this as possible. recently got a Wii U. It is an 8gb model, so I needed to connect an external HDD drive. I still had one laying around. Only a few months old, once put some files on it, never used it much or actively, 1Tb in size, no external power supply (though I got a USB-Y cable for it).
I decided to take the files off it, and format it on the Wii U. Before the HDD I had a standard 16Gb USB-stick connected to hold me over. I copied all the files from the stick to the HDD, disconnected the USB-stick (in the recommended way of course) and booted up the console again. Everything seemed to be fine. I then booted up Smash, went to the trophy gallery, left, and the system crashed. It gave me an error message saying that there was a problem with the HDD.
I rebooted the console and started Smash again. This time, I wanted to test whether I could trigger another error (that way I could be sure there was a problem). I went into 8-player Smash, loaded nothing but characters that were on the HDD (DLC and Miis), battled, won, nothing happened. Then I went to the eShop and decided to download the Starfox Guard demo, since I heard the eShop gives issues with broken HDDs as well. However, it's downloading just fine right now with no issues.
Naturally, I'm a little worried now. I don't want to continue using this HDD if it may end up giving problems. Has anyone ever had anything like this? Could the problem be with Smash? Or is this just a coincidence?
UPDATE: Never mind about Starfox, I just got an error message, the HDD apparently can't handle any new data. Please help!
ANOTHER UPDATE: Just tried to install a smaller demo (Word Puzzles by POWGI). That one installed fine. I'm completely lost as to what's going on here. Please help!