I encountered an unrecoverable error immediately upon loading the game when placing a blueprint containing elevated rails. The blueprint uses only ghost entities to create spacing, which I need because I am playing in a narrow world.

Factorio - Space Age 2.1.9

O mod Subsurface - build beneath your base! (1.1.27) caused an unrecoverable error.
Please report this error to the mod author.

Error while running event Subsurface::on_player_cursor_stack_changed (ID 37)
LuaRecord doesn't contain key is_blueprint_preview.
stack traceback:
[C]: in function 'index'
__Subsurface/scripts/elevators.lua:122: in function 'elevator_on_cursor_stack_changed'
Subsurface/control.lua:671: in function <Subsurface/control.lua:670>

I get the same error when loading blueprints just the suspended tracks, without the ramps. I think it’s an issue with all the structures from the elevated tracks DLC.

O mod Subsurface - build beneath your base! (1.1.27) caused an unrecoverable error.
Please report this error to the mod author.

Error while running event Subsurface::on_player_cursor_stack_changed (ID 37)
LuaRecord doesn't contain key is_blueprint_preview.
stack traceback:
[C]: in function 'index'
__Subsurface/scripts/elevators.lua:122: in function 'elevator_on_cursor_stack_changed'
Subsurface/control.lua:671: in function <Subsurface/control.lua:670>

I ran some more tests, and these errors occur with any blueprint I try to load. Sorry for flooding the forum.

Thanks I'll fix it in the next release