Also what are your gathering rates? And also how many people are on during these lag spike times?
My gathering rates are x10 but I set the harvesting to 1 in my gameusersetting.ini and in my game.ini I set each resource with HarvestResourceItemAmountClassMultipliers.
Its weird though, this lag was just like a flip of a switch. It had 20 people on but it always averages around that. When I say lag it was more like freezing and when it would stop lagging or freezing it would only be for like 5 seconds and people would keep getting disconnected too.