newsbin.com

Definitely not a big problem, but sometimes after download finished and the rar got repaired and extracted correctly, some *.nb2 are left behind and not deleted automatically I don't know why

I do. NB2 files are going away in the future.

Here's what happens.

1 - You download a non-compacted set.

2 - Newsbin starts repair before the last file finishes.

3 - Repair repairs one or more of the downloading files into existence.

4 - After the repair completes, the download never finishes and leaves an NB2 around.