I found garbage pixels in the railway brick slope approaching the iron bridge. (´・ω・`)
(https://i.imgur.com/7wOfU8W.png)
That look's like when they did the image file, they forgot to change those area's to transparency.
Thank you for that report - I believe that I have now fixed this. TheRoadmaste1996 was correct: these were images caused by incorrect transparency being set for some pixels.