Is it possible that he lag only occurs if someone is in a specific area?
My thought at first was that we had alot of mobs in general in one area so i tried clearing them and leaving as few as possible, that didn't really solve anything. So even if im at a biome that i haven't been before and has no mobs or structures it will still lag. I don't think there's specific areas that it happens. Just sometimes the lag stops for a minute or two and then starts again