I am now in Chapter 2, and I've encountered a strange bug. In some sewer battles, when Geralt kills his opponent, the game slows down terribly, almost to a stop. A bit later it picks up the normal speed again, but during the slow-down monsters continue to chew on Geralt. Also a monster killed with such a slowdown doesn't drop any loot.

Also there's a variant of (probably) the same, when in a particular part of the sewers the game slows down on encountering an enemy and remains very slow until Geralt leaves the area.

Perhaps someone knows how to cure such slowdowns?