In technologies.lua change:
icons = {{icon = icon, tint = tint}},
icon_size = 128,
to:
icons = {{icon = icon, icon_size = 128, tint = tint}},
this will fix technology icon.
Also, could remove local technology_icon and local technology_icon_size from furnace-vanilla.lua and put the values directly in technologies.lua same as item or entities have (actually data.icon_size is never read in technologies.lua anyway).
