There is a really annoying bug when dual wielding the penetrator, and using a gamepad. When firing at enemies the player suddenly changes direction.
According to the steam forums, there is a beta build accessible if you have the game on steam which fixes this issue. Is there a beta build available for the GOG version. Developer, please help... Thanks

I have the same bug! This happens to me when I'm using an Xbox 360 gamepad. On keyboard + mouse the bug doesn't happen. Unfortunately gamepad support is still broken in this game.