In Chapter 4 when you go to find the key two logbook entries are present simultaneously, one of which tells you that you've found the key when you haven't.
Also, more of a suggestion than an error, I've been confronted with several places in game where your logbook entries make absolutely no mention of where to go for your next objective. If you've only been testing internally I can see how you might think it should be obvious but you should really be trying to see it from the perspective of a player who might put your game aside for a week or two and come back.
The Latest GOG update to 1.0.5 still shows v1.0.0 on the title screen.
I'd also like to add that you really should get rid of the mouse cursor when a gamepad is detected.
I'm on Windows 10.