From my testing, the broken shadows seem to more easily occur in maps with high display sizes (especially the ones going over 10000). Custom Items with bad optimization seem to be able to cause this issue as well. Some blocks seem to be more affected by this issue than others (4-6-2 being the most obvious one). Nevertheless, once reaching a certain point, even normal road blocks such as 2-1-5 will be affected by the same issue.
