> Contents of logfile CRASH.txt:
> "HTTrack 3.33.21 closed at 'Devhtsback.c', line 233
> Reason:
> assert failed: !duplicateEntryInBacklog"

Probably due to the following scenario:
- a link A aready downloaded
- a data (image, for example) link B redirecting immediately to A 
- A being re-added

I tried to reproduce the issue, using:
<http://private.httrack.com/redir>

but I couldn't crash the a6.

Can you tell me the site's name where you encountered the problem ?
Anyway, I will add in -a8 additional tests to ensure that no link already
downloaded is added.