The locations have been almost everywhere I've ever been on the map. Off the top of my head as mentioned earlier, the row homes southeast of rosewood city, the storage building east of Rosewood city next to the farms. In fact I've had this problem most the time when a storage building is involved. The second story of the city hall building in Rosewood. I'm mostly naming Rosewood here but it really happens everywhere on the map. I try to destroy a section of wall that is unobstructed on both sides and it just won't allow it from one side but it does allow it from the other. It happens so often that I don't really think about it anymore. It's just something I got use to living with. I'll start taking screenshots and jotting down locations when it happens so I can provide some good examples for the team to fool around with.
I have an experiment for you,
A great example of this would be a storage building. You know the ones loaded with crates. Those buildings are two story's tall but there's no second floor. Find two of them located adjacent to each other and build stairs and a bit of second floor in both buildings. Now try and knock down a section of wall so you can make a second story walkway from one building to the other. If it shows that it's going to allow you to destroy a section of wall then don't. Go to the adjacent buildings second floor and try destroying a section of wall and making a second story walkway from that building. You'll find one buildings going to let you do it and the other won't.
I think this is a great example because there are no obstructions on the second floor guaranteed. Why, because you just built the second floor yourself. There's nothing there that you didn't put there. Do you follow me?
Yeah it's the Fossoil southwest of Rosewood, I usually make at least a safe house out of every Fossoil Station I come across. This time I went a bit crazy with it and built a full blown base. I built a ton of storage and a single enclosed bedroom on the roof. Normally I locate my main bases as close to city center as possible then a series of safe houses in a radius from my main base. I decided to change it up a bit since I started a new game with the PZ40.40 release. I've located my main base outside town this time and I'm driving into town to scavenge. It hasn't been to bad so far.