Packet loss and lag for all players when connecting a new player

I've noticed strange behavior on my server. When a new player connects, all players show packet loss and lag occurs. The most interesting, lag occurs only after the player has downloaded the map. In this way, it has nothing to do with network quality and bandwidth overflow. I noticed the same behavior on other large xonotic servers as well. Therefore, it is probably possible to rule out a problem with my server. The usage of one cpu core does not exceed 30%. There is no swapping or interrupting the processor. The lag appears around the time of the "username connected" message.

sys_ticrate = 0.0166667