Failed to load mods: Error while loading entity prototype "upcycler" (furnace): Value must be a list in property tree at ROOT.furnace.upcycler.graphics_set.working_visualisations
Modifications: Upcycler

It is probably related to this in the changelog.

Modding
Changed working_visualisations to enforce that the provided array is contiguous.

I temporarily fixed this by changing data.lua from %AppData%\Roaming\Factorio\mods\upcycler_1.1.8.zip

Line 120 and 121 I replaced with this:

table.remove(upcycler_entity.graphics_set.working_visualisations, 2)
table.remove(upcycler_entity.graphics_set_flipped.working_visualisations, 2)

It works now.

fixed in 1.1.9