Nether glitch, getting attacked by invisible and unattackable mobs (zombies/skeletons)

Sometimes when going thru the nether portal from the overworld to the nether in my realms world. Players get shot by skeletons or attacked by zombies. Both of which are not even visible. Nor can I seem to repel the zombie attack with a sword. This results in certain death as my server is on the hard difficulty. This is incredibly frustrating.
I noticed it seems to happen mostly by going in the portal at night.

Steps to Reproduce:
1. Play on Minecraft Realms
2. Enter Nether Portal
3. Randomly get screwed over by mobs that are not there