Revealing mistake: When Frasier comes into the chalet after skiing he doesn't show any of the visible effects after a hard day on the slopes. Meaning, his face isn't even flushed from the cold, his hair is perfectly combed after wearing a hat and there is not even a drop of snow on his boots.
Revealing mistake: When Jerzei is coming through the door with an axe, you can see the door is paper thin to make it easier to get through. In fact you can see Alexei Sayle being very careful to only chip small bits away because a decent whack with the axe would smash the whole thing down.