This seems to be a change from 42.14.0. Looking at the logs, the reason seems to be automatic backups taking too long and the server killing itself due to no response:
[19-02-26 00:06:39.019] LOG : General command entered via server console (System.in): "ping@pong".
[19-02-26 00:06:44.127] LOG : General command entered via server console (System.in): "ping@pong".
[19-02-26 00:06:49.133] LOG : General command entered via server console (System.in): "ping@pong".
[19-02-26 00:07:51.344] LOG : General compressionElapsed=55959ms, mergingElapsed=1681ms.
[19-02-26 00:07:51.470] LOG : General Backup made in 57767 ms.
[19-02-26 00:07:51.471] LOG : General ItemPickInfo -> cannot get ID for container: inventorymale.
[19-02-26 00:07:51.472] LOG : General ItemPickInfo -> cannot get ID for container: inventoryfemale.
[19-02-26 00:07:51.507] LOG : General Coop master is not responding, terminating.
[19-02-26 00:07:51.528] LOG : General command entered via server console (System.in): "ping@pong".
[19-02-26 00:07:51.578] LOG : General Shutdown handling started.
[19-02-26 00:07:51.578] LOG : Network Server exited.
[19-02-26 00:07:51.668] LOG : General SaveAll took 89.3694 ms.
[19-02-26 00:07:51.871] LOG : General Saving players.
[19-02-26 00:07:51.892] LOG : General Saving worldgen params.
[19-02-26 00:07:51.905] LOG : General Saving GlobalModData.
[19-02-26 00:07:51.916] LOG : General Saving finish.
[19-02-26 00:07:51.917] LOG : General Saving took 338.3808 ms.
Looking at earlier logs from 42.14.0, backups were much faster:
[18-02-26 13:53:46.189] LOG : General compressionElapsed=1869ms, mergingElapsed=1974ms.
[18-02-26 13:53:46.284] LOG : General Backup made in 3939 ms.