Mobs taking an extra long time to spawn

If you are on a Minecraft Realm, there is a significant issue with how mobs are generated. If you travel at a high speed (through elytra usage for example), mobs will cease to spawn in properly. many mobs will fail to load into older chunks, and new chunks will fail to generate any passive mobs. (speculation) I think this has something to do with the changes to rendering/the world being optimized.