game freezes in multiplayer when new chunks are loaded

What I expected to happen was...:
Nothing should happen.

What actually happened was...:
When a player explores or travels, resulting in any new chunks being loaded, the entire server will freeze for several seconds, cpu and ram load goes up to 100%, freezes for all players currently online, all mobs, entities and actions are halted. Only in multiplayer, does not happen in single player when exploring.

Steps to Reproduce:
1. more than 1 player online in multiplayer
2. one or more player/s loads new chunks by either travelling or teleporting.