Tested in new world and old world.
Problem happens earlier in old worlds.

I tested it with this Command:

 /particle happyVillager ~ ~5 ~ 0 0 2 0.01 10

Commandblock is in repeat-mode (activated via Redstoneblock).
In old worlds you need only 5 Commandblocks running this or any other Command like /testfor @e - in new worlds it needs up to 20 Commandblocks.

It needs vom 30s to 5 min to have those lags.
When the lags appear Mobs seem to be in slowmo.

commandBlockOutput is false