[Dev 2513] Error: attempt to concatenate a nil value

just got that error again but this time after starting a building

develop-2513 (x64)
stonehearth/lib/i18n/i18n.luac:11: attempt to concatenate a nil value
stack traceback:
	radiant/modules/common.luac:32: in function <radiant/modules/common.luac:32>
	stonehearth/lib/i18n/i18n.luac:11: in function 'format_string'
	stonehearth/lib/game_master/game_master_lib.luac:5: in function '_compile_bulletin_text'
	stonehearth/lib/game_master/game_master_lib.luac:9: in function 'compile_bulletin_nodes'
	...er/controllers/encounters/dialog_tree_encounter.luac:4: in function 'start'
	...rvices/server/game_master/controllers/encounter.luac:22: in function 'start'
	...rth/services/server/game_master/controllers/arc.luac:49: in function '_start_encounter'
	...rth/services/server/game_master/controllers/arc.luac:41: in function '_trigger_edge'
	...rth/services/server/game_master/controllers/arc.luac:17: in function 'trigger_next_encounter'
	...me_master/controllers/encounters/wait_encounter.luac:11: in function '?'
	radiant/modules/common.luac:86: in function 'invoke'
	radiant/controllers/timer_controller.luac:29: in function 'fire'
	radiant/controllers/time_tracker_controller.luac:9: in function <radiant/controllers/time_tracker_controller.luac:9>
	[C]: in function 'xpcall'
	radiant/controllers/time_tracker_controller.luac:9: in function 'set_now'
	...earth/services/server/calendar/calendar_service.luac:112: in function 'fn'
	radiant/modules/events.luac:79: in function <radiant/modules/events.luac:78>
	[C]: in function 'xpcall'
	radiant/modules/events.luac:78: in function 'trigger'
	radiant/modules/events.luac:97: in function '_update'
	radiant/server.luac:19: in function <radiant/server.luac:17>

in addition with this error from the scaffolding_manager

develop-2513 (x64)
...earth/services/server/build/scaffolding_manager.luac:49: assertion failed!
stack traceback:
	radiant/modules/events.luac:68: in function <radiant/modules/events.luac:65>
	[C]: in function 'assert'
	...earth/services/server/build/scaffolding_manager.luac:49: in function '_trace_rblock_region'
	...earth/services/server/build/scaffolding_manager.luac:33: in function '_add_region'
	...th/services/server/build/scaffolding_builder_1d.luac:48: in function '_add_scaffolding_region'
	...th/services/server/build/scaffolding_builder_1d.luac:53: in function '_update_status'
	...th/services/server/build/scaffolding_builder_1d.luac:40: in function 'set_active'
	...th/services/server/build/scaffolding_builder_2d.luac:43: in function '_update_status'
	...th/services/server/build/scaffolding_builder_2d.luac:37: in function 'set_active'
	...arth/components/fabricator/fabricator_component.luac:213: in function '_start_project'
	...arth/components/fabricator/fabricator_component.luac:121: in function '_updates_state'
	...arth/components/fabricator/fabricator_component.luac:117: in function 'obj'
	radiant/modules/events.luac:15: in function 'self'
	radiant/modules/events.luac:80: in function <radiant/modules/events.luac:78>
	[C]: in function 'xpcall'
	radiant/modules/events.luac:78: in function 'trigger'
	radiant/modules/events.luac:97: in function '_update'
	radiant/server.luac:19: in function <radiant/server.luac:17>

the building job I issued wass the short connection paths between the doors and the main road (which is already getting built)

edit:
well as you can see there is a staircase carved in the wall in the background…
before the error happened it was already finished and covered with white wood floor slabs and after the error popped up the white wooden slabs covering the stairs went invisible…
they are still there because I can’t place new ones… for some reason you can’t see the red “X” mouse icon when I try to place new floor slabs on the staircase on the screenshots

but after save/loading the staircase is shown correctly again