I assume that some of these findings are redundant and I hope I listed them accordingly.
I wondered if the "missing" walls may in some case due to an empty slot J in the wall template, but I checked this for some walls and it seems to be independent from that.
I see there is a pattern in so far as often the most distant wall on the left side close to the 3d-view center shows a wrong section of the wall template (a "wall fragment", maybe sometimes a transparent area), and after making a side step, turns to magenta. Naturally, I may overlook some of these artifacts if they are hidden by other walls...
Square 5,9,S: "Conifer Wall" not visible (transparent section?)
Square 6,11,S: "Conifer Wall" magenta
Square 8,12,N: "Rock wall" wrong section/slot shown
Square 6,8,E: same
Square 10,14,N: same
Square 10,13,N: same
Square 9,12,N: same
Square 11,14,N: "Rock wall" magenta
Square 21,12,S: same
Square 22,11,S: Solitary tree missing
Square 27,17,E: same
Square 22,11,S: Solitary tree magenta
Square 27,18,E: same
Square 25,16,E: Hut door wrong section
Square 25,17,E: Hut door magenta
Square 25,24,E: Hut side wall wrong section
Square 25,25,E: Hut side wall magenta
Square 18,29,E: River magenta
Square 26,24,S: River magenta
Interestingly, it seems to me that in case of the river wall, the "wrong section" problem does not occur, but I am not sure.