When I try to use the experimental:luafurnace, the game crashes almost immediately after placing it. When I log back on, the map is reverted to before it was placed. The last bit of my debug.txt: debug.txt.
I have the latest git version, updated just minutes ago. Before, I couldn't even get the luafurnace. Now I can get it and place it, which is when the crash occurs.
Ah in that case could you paste your debug.txt file contents here so we can see whats happening.
It also might be worth to first delete your debug.txt file then restart minetest place the furnace then once it crashes paste that new debug.txt file (if its quite big you could use pastebin.com or some similar service)