Unfortunately I received the below non-recoverable error/crash with version 2.0.41. I think it was a background script since I wasn't in combat at the time and there weren't any enemies that I know of in render distance:

The mod Enemy Race Manager (2.0.41) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event enemyracemanager::on_script_trigger_effect (ID 171)
enemyracemanager/lib/boss_processor.lua:712: attempt to compare nil with number
stack traceback:
enemyracemanager/lib/boss_processor.lua:712: in function 'assisted_spawner_spawns'
...yracemanager__/controllers/on_script_trigger_effects.lua:118: in function '?'
...yracemanager__/controllers/on_script_trigger_effects.lua:235: in function 'handler'
core/lualib/event_handler.lua:72: in function <core/lualib/event_handler.lua:70>

Hi

May you send me your save?

If you ain't fighting the boss, that function shouldn't run. Maybe a mod changed the autoplace control of the hidden spawner, which caused it to spawn.

+1

2.0.42 should fixed it.