I am trying to create a spanned zip to a non-removable drive with some given size and when I do that with a zip filename that ends in .bk2, the zip component will not automatically change the zip extension for each volume. What happens is that as each volume is created, it overwrites the volume that was already there. It doesn't seem to matter what value I pass in to the SpanMultipleDisks property, I get the same behavior if that's set to xdsAlways, xdsNever, or xdsRemovableDrivesOnly. I am setting the SplitSize64 to a valid value so I can control the volume sizes on the disk.
When I change the extension to something that doesn't end in a number (like .bk) then it works fine. I'm not sure where I should submit bugs, so if this is the wrong place please let me know and I'll re-submit where I need to.