I often have visiting sims knock on the door from the inside. I had assumed that it was because the door was placed the "wrong way", but it says in one of the above comments that they should be able to recognise the outside regardless of which way the door is placed, which makes sense since the door can be placed either way. I like to have 2 doors at the front of some houses with the handles together in the middle, and this is when I notice the visitors going inside to knock. I also think it only happens on lots where I have built the house, but I don't play many of the pre-existing ones, so can't be sure.
Certainly still happens to me though (today).
I think a couple things might be happening here from what I've read.
I've had this happen to one of my homes recently. The house has multiple doors leading to the outside.
When it happened to me, the sim went in through a secondary door and knocked on the inside of the front door.
My suggests are:
1. Be sure to click on the door that you want used as the front door and be sure that Set As Front Door is greyed out which means it is already set as the front door. If it isn't, then click it.
2. For that door, be sure that in build mode the arrows on the door point outside, not inside.
Since I took these steps, I've had no more issues with them going to the wrong side to knock.
