Iron to matter factory produces liquid matter,. but copper to matter factory produces nothing - the matter factory works as with iron, it just doesn't produce any output.

What is your version of the game and mod? "Liquid Matter" has long been renamed into "Matter" and I don't have this error.

The very latest, and yes, its only called matter now, but the rename was not that ago :)

Seems it's another of these rotation/blueprint bugs that plague krastorio - it apparently happens when bots build the factotry. When rotating four times, or removing/rebuilding, it starts working properly again.

Could u use Krastorio 1.2.18 and tell me on that version step by step how reproduce the bug?
This is the recipes interested:
{
type = "recipe",
name = "copper-to-matter",
category = "matter-extraction",
icon = krastorio_recipes_icon_path .. "copper-m.png",
icon_size = 32,
energy_required = 2,
enabled = false,
hidden = true,
ingredients =
{
{"copper-ore", 20},
},
results=
{
{type="fluid", name="k-matter", amount=10}
},
subgroup = "matter-re",
order = "c[copper-to-matter]",
},
{
type = "recipe",
name = "matter-to-copper",
category = "matter-usage",
icon = krastorio_recipes_icon_path .. "m-copper.png",
icon_size = 32,
energy_required = 1,
enabled = false,
ingredients =
{
{type="fluid", name="k-matter", amount=10},
},
results=
{
{type="item", name="copper-ore", amount=20}
},
subgroup = "matter-ru",
order = "c[matter-to-copper]",
}

How u can see result is defined so will produce an output. If I haven't more details about that seems work, maybe u have found another bug