Necrovision: Lost Company - falling through floor

[Dandi8]

Hey,
I just bought Necrovision: Lost Company from Green Man Gaming, installed it, clicked New Game and the first thing I see is my character falling to his death, the map above him and an endless pit of nothing under him.

Basically, I fall through the floor every time I start a new game (or the floor doesn't exist, I dunno).

How to fix this? I'd like to play