It seems that Havoc 11 has at least some amount of manual steel, considering when I tried to use a basher to stop a builder, the "clink" sound was played.
The replay plays up to the point where I noticed this.
There's nothing wrong with the level here. The problem is that the basher is very steel-sensitive. The behaviour has been changed for future updates to remedy this; it just may be a while before those are released (outside of experimental versions, which are already available).
Earlier discussion of NL basher. Including the amazing Bow before the holy Cow. (http://www.lemmingsforums.net/index.php?topic=2579.0)
-- Simon