Check out this bugtracker from Spigot, the server software developers: https://hub.spigotmc.org/jira/projects/SPIGOT/issues/SPIGOT-1626?filter=allopenissues
There you can see that Mojang is responsible. We hope that the devs of Spigot can fix it but it takes time. Keep in mind, we’re pre-generating the map to lower the lag issues to a minimum. It will take 2-3 more days!