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.
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