I was logged into my Minecraft Realm and was suddenly kicked with "server closed" I checked to make sure that the servers were not down and that I have a current subscription. Once I rejoin, I was at the original spawn (I moved the spawn chunks) with not items. I travelled back to my ocean monument base and it was full of hostile mobs.

The Minecraft wiki states that hostile mobs do not spawn in ocean monuments and I checked the update page to see if a changed had happened. I moved away over 120 blocks to make sure all the mob despawned incase it was a single time problem, but on returning hostile mobs spawned again

I could not recreate this issue in Single player