On my first playthrough the person who wants you to deliver a letter did not give me any package, so I couldn't get past 90%.
On my second playthrough, I knocked on the door where you start last of all, and the person told me I had already received a package, but he gave me a part anyway and at the same time the house to the left also gave me another part. So I got the generator to 110%. Luckily I was still able to see the good ending so I didn't have to play through a third time.
Nice atmosphere but not very fun gameplay.