The mod Castra (0.4.3) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event castra::on_tick (ID 0)
Unknown entity name: castra-enemy-railgurret
stack traceback:
[C]: in function 'find_non_colliding_position'
castra/base-generator.lua:592: in function 'place_turrets'
castra/base-generator.lua:670: in function 'create_enemy_base'
castra/base-upgrades.lua:35: in function 'upgrade_type'
castra/control.lua:618: in function 'randomly_upgrade_base'
castra/control.lua:669: in function <castra/control.lua:665>
They do seem to be working better though, new stuff is popping up!