If using a 3d furnace , furnace_on turns 3D object into a simple cube instead of just applying furnace_on texture on 3d object.
Animated furnace not working too anymore.
MC-69545
Furnace off / on display error
Resolved
Invalid
0
they are two diffrent blocks, minecraft:furnace, minecraft:lit_furnace, diffrent blocks require diffrent models, however, not sure about the animated part