Using a server.jar after 1.12-pre2 creates massive lag in the server.

Time between ticks is normally 1-10ms in Minecraft 1.12-pre2 and previous versions. In 1.12-pre3 and 1.12-pre4, the time between ticks jumps to 20-100ms, with no changes to the world file, and no changes to the server files.

Please Note: There is NOT an actual error code, however, this is a BIG issue as I cannot play on a server past 1.12-pre2 now.