Regarding 31cb............................ folder with part.31 inside it, make sure your temp folder is not the same as download folder.
This  next to the folder makes me think that you're importing nzb files to altbinz directly from browser.
You have few options:
- Select all parts from that thing you want to download and then make single nzb which you'll import into altbinz. (In the case you mentioned you for sure imported 2 nzbs, one with rar and par2 files and the other with srr/sfv/nfo)
- Use altbinz internal search tabs, select everything belonging to that thing and then press ctrl+d
- Do as you did before, but before starting download, go into download queue tab, where you'll see for sure same names as you described:
Select both collections and press CTRL+J to join them into single collection.