Starting a new game of Seablock, Milestones crashes immediately upon loading to map with the following error:

Modi Milestones (1.3.18) aiheutti virheen, josta on mahdoton palautua.
Ilmoitathan tästä virheestä modin kehittäjälle.

Error while running event Milestones::on_player_created (ID 26)
Unknown item name: landfill-sand-3
stack traceback:
[C]: in function 'get_input_count'
Milestones/scripts/milestones_util.lua:311: in function <Milestones/scripts/milestones_util.lua:294>
(...tail calls...)
Milestones/scripts/milestones_util.lua:273: in function <Milestones/scripts/milestones_util.lua:260>
(...tail calls...)
Milestones/control.lua:83: in function <Milestones/control.lua:79>

Narrowed it down to minimal modlist, all part of Seablock modpack:
angelsbioprocessing
angelspetrochem
angelsrefining
angelssmelting
bobelectronics
bobenemies
boblibrary
boblogistics
bobores
bobplates
flib
Milestones
SeaBlock
SpaceMod

Basically, minimum required dependencies of Seablock plus the combination of SpaceX and Bob's enemies. Either SpaceX or enemies in itself works fine, but add both and it'll crash.

Edit: Seems to work fine with the Feoras forked version of SpaceX. I'll use that for now, seeing that the base version seems to not be updated, although still included in Seablock modpack.

Accidental double

Did some debugging myself, the issue seems to be with combination as above, which triggers the Sea Block Pack setting, but if Landfill Painting is not enabled, it won't find landfill-sand-3 and crashes. Feoras fork for SpaceX is of course named differently, and thus doesn't trigger the error as it doesn't load the preset with containing the tile which would crash it.

Thanks. I do agree that there is a Milestones issue, it shouldn't crash even if an item from a preset doesn't exist. I'll take a look when possible.