1 - Fill any backpack (30 slot or 35 slot) full of items.
2 - Put the full backpack inside of another backpack (it should take up 25 slots, leaving either 5 or 10 left in the empty backpack.
3 - Keep filling up other backpacks of items and putting them in other backpacks.
4 - Desync begins to occur for yourself very badly, not allowing to use hotkey commands 1 through 0, vaulting, opening doors, etc.
5 - Other plays in the vicinity (proximity) also begin to experience lag/desync issues, however if they go far from you, things begin to smooth out.