Game crash when entity goes through nether portal

When entering the nether after an entity that isn't a player goes through a portal, the game crashes. This is different than the game just crashing when a player enters a portal. The only solution I've found is to switch to peaceful mode and wait five minutes for whatever passed through the portal to despawn. This is because when you switch to peaceful it doesn't automatically despawn hostile mobs if they are in the Nether until you go into the Nether.