It's been a while sorry. I hadn't forgotten about this, but I hadn't had a chance to look at it either.
I was able to reproduce this issue and it has been reported to the developers for investigation.
I did some further testing and it only seems to affect snapshots that are long vertically. I was able to reproduce the issue in another area of your world (the Jungle) and saw part of the background was cut off. Strangely even with this information, I could not reproduce it on another world, making me wonder if it was something in particular about this world with problems.
As a workaround, you could try shrinking the snapshots so they are not as tall. Multiple snapshots could be aligned together in an image editing program. In-game screenshot functionality also worked as expected if you want screenshots without the UI/HUD in the way.
I also really liked your buildings! I can only dream of making something that looks so nice!