Another error with the popular Planet Maraxsis Mod. I am not there yet, so i disabled Maraxsis for now.
https://mods.factorio.com/mod/maraxsis

Failed to load mods: Error in assignID: item with name 'maraxsis-hydro-plant-extra-module-slots' does not exist.

Source: maraxsis-hydro-plant-extra-module-slots-upcrafting-1 (assembling-machine).

The same error:
Не удалось загрузить следующие моды: Error while loading entity prototype "cerys-fulgoran-cryogenic-plant-upcrafting-1" (assembling-machine): Key "item" not found in property tree at ROOT.assembling-machine.cerys-fulgoran-cryogenic-plant-upcrafting-1.placeable_by
Modifications: No More Gambling › Maraxsis

This should also be fixed properly now, you can't place the power plant yourself so the placeable_by array was empty, which Factorio was complaining about.

https://cdn.discordapp.com/attachments/1219946617592090644/1330495509575503943/image.png?ex=678e3000&is=678cde80&hm=4227813fe942f0648b6988e5d014253d4bf66473eb3dfa9008469d6e137b7148&