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This could be because of how busy it is during prime time nyzul activities on your server. Although assault is made so multiple groups can in essence enter a seperate "server" to do their own run while others do it simultaneously, I wouldn't doubt a for a second having many people in the same zone technically could cause connection issues to others.

Try doing your Nyzul run at a slightly different time to see if it helps. If not then it most likely is a minor connection issue on your end.