Guesting?
You are basically on the server in all respects besides wvw so naturally if a lot of people are guesting overflow will be more common.
Ugh, its really screwing with world boss events. Ran into 2 overflows on tequatl and Shatterer. Since the new loot drops.
The overflow depends on the map… Guest are considered as additional number.. Based on the details you cant enter if the server is full