We verified this was a bug when importing with ANY Brand, not just Unknown or Custom Assembly.
The problem turned out to be the new feature we added that automatically incremented the BookID. The Brand-DiscID-BookID fields are so intertwined that a simple change broke the DiscID field. We reviewed the code for hours and understand what is happening, but can't find a simple way to fix it.
As a result, we have removed the new Auto-Increment on the BookID field so it works like 2.212 and prior.
We now have a new 2.213 Release #2 available for download. Please click your Hoster download link to get it.
If you want to do some importing right now, you can enter the DiscID BACKWARDS
.... and it should work. However, we'd rather you download the new to make sure some other bug is not lurking. This is one that got past all of us!!!