Are you using MOO to place your objects ?
There are no split levels within the areas where the problem occurs and the only objects which overlap are non-routable décor such as computer stacks which are placed outside of areas where sims pass each other.
Have you tried repairing your game and deleting your caches ?
This is only a problem at club events where sims frequently pass through the DJ booth or share slots while participating in related activities.
Are you using mods in your game ?
This is most noticeable with high occupancy mods [I've tested this with up to 50 participants] however it occurs randomly at any volume when all characters approach a single object such as the DJ booth.
Do you get actual routing failures with stumping, waving and dropping of queues or just them routing through each other ?
The queues aren't dropped and the sims don't report obstruction, they simply pass through each other or interact with each other at distances. This occurs frequently while large groups are interacting within small rooms which contain attractive objects such as televisions or stereos.