This now has happened several times in the 1.13 pre6 release. Every time you repeatedly trade paper for emeralds with a cartographer villager, the server will eventually give a time-out, and all players will be disconnected. The server itself does not crash, and no stacktraces can be found in the server log. It does say this though:
[23:44:07] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 39074ms or 781 ticks behind.
That message only appears in the logs when this timeout happens.
Environment
Server java version: openjdk version "1.8.0_171"
OpenJDK Runtime Environment (build 1.8.0_171-b10)
OpenJDK 64-Bit Server VM (build 25.171-b10, mixed mode)
Client java version: java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)
This bug can be reproduced consistently. Set up a few cartographer villagers, keep trading paper for emerald so they will unlock new levels of trade, and eventually this will happen:
[11:46:32] [Server thread/INFO]: Xena_Dragon lost connection: Disconnected
[11:46:32] [Server thread/INFO]: Xena_Dragon left the game
[11:46:32] [Server thread/INFO]: Dongersmooi lost connection: Disconnected
[11:46:32] [Server thread/INFO]: Dongersmooi left the game
[11:46:32] [Server thread/INFO]: Joene lost connection: Disconnected
[11:46:32] [Server thread/INFO]: Joene left the game
[11:46:32] [Server thread/INFO]: Nomicor lost connection: Disconnected
[11:46:32] [Server thread/INFO]: Nomicor left the game
[11:46:32] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 35350ms or 707 ticks behind