Just Dance 2 Special Edition says "Can't open BigFile"

[SCOTT0852]

I'm using 5.0-10474, I dumped a copy of JD2 Best Buy edition a while back for Redump and decided to try playing it today, but as it was in split 2gb parts from Cleanrip I pointed Wii Backup Manager at the SD2Y41.part0.iso and told it to convert to a .WBFS as I was getting a "Can't open BigFile" error when I was just running the part0.iso. It created a 3.15gb file, so I don't think I converted it wrong. However, the WBFS version gives me the exact same error. The screenshot button in Dolphin doesn't work on this screen for some reason.

Is this just a bad dump sorry Redump or is something about the Best Buy edition different enough to make it fail? Or am I just a complete noob with Wii Backup Manager?