In all of the SG maps, there are blocks that are placed illegally - that is they can't be placed like that in vanilla Minecraft. When broken, these blocks will not be replaced as legally placed blocks would, but instead will remain destroyed along with all adjacent illegally placed blocks. This behavior is commonly seen throughout SG on many servers, and is not itself a problem.

However, the map SBS City has a field of sunflower stems towards the edge of the map which when one is broken, all become broken as described above. Because of how many there are, any player who breaks them will get kicked for spam.

Video: https://youtu.be/yvrhJIgW66k
To recreate, go to this location and break one of the stems.