OlausPetrus: I didn't have any technical problems with that scene or any other sex scene in the game. However I think that especially that Lukas and Carla sex scene was unnecessary and bit awkward. The plot would have worked better without that romance.
Puda: I agree. Anyway I have tried to do the chapter again two times and the sex scene actually worked. I guess the game has some bugs from time to time.
I liked the game though even if I finished it in 6.30 hours.
The game seems to have occasional glitches, which don't happen frequently. I had to restart one of the earlier chapters, because something went wrong and there was a glitch.