I can't attach body parts and after the lights go out the game becomes dark, no flashlight or anything to progress

Hi.

You can complete the body before the lights go out. Have you tried that?

All the bodyparts are spawned before it becomes dark, so it's easy to complete.

It doesn't get attached to body no matter what I do

The body part disappears while updating, and the game doesn't proceed

Yea i tried E, mouse buttons and anything I could think off. I can never get the first arm to attach but did get the speed run option to work after some messing with the settings

Same happened to me, I didn't attach the body parts and eventually the lights went out and I had a arm in my hand, with no flashlight (flashlight wasn't working because I was no longer holding the gun).  There was only a couple of sources of light in the distance (the lit up train notification led for example), the pause button stopped working, I was struggling to progress so had to quit the game.  Hopefully gets patched before steam release.  

Great demo, really impressed by the realism.  I watched the full play through via Fooster on Youtube (random video recommendation), and was glued to the end.  I had to download it.  I've just been playing resident evil 3 and alan wake, so I had to try this, and it is on a whole new level of horror.  Can't wait to see more!

Performance wise : I'm able to get average of 60 fps with this setup :

Ryzen 5800x3d, rtx 4080, 32gb ram, dlss enabled in game, 2560 x 1440, 100% scaling, max graphics.