I'm not an expert or anything, but I'm pretty sure sex isn't supposed to work this way. (NSFW warning!)
Check out what happens when Chris Klos encounters a really bizarre glitch during a sex scene in The Witcher 3. Limbs and heads start detaching from bodies, the camera angles goes out of whack, and eventually Geralt just fuses with the sex worker. It is the strangest and most hilarious thing I've seen in the game so far.
That said, after seeing how similar the sex scenes with minor characters are in this game, this sex glitch could be considered a big improvement over the original scene.