Iron can be duplicated and Propeller Bench causes crash.

[nickseo7]

*English is not my mother language, so be aware of that there can be some grammatical errors.

As 1 Iron Rod can be broken into 1 Iron Ore Piece, we can make 4 Iron Ore Chunks with 16 Iron Bars from 6 Iron Ingots. If the chunks get ground and smelted, it results 8 Iron Ingot, which means duplication.

Another way of duplicating iron, make 6 Iron Rods using 3 Iron Ingots through Lathe,

craft 8 Iron Bars with rods. The bars are equal to 4 Iron Ingots with the same way above.

Also currently the Propeller Bench crashes the game when placed down, but Minecraft Flight Simulator has been updated to Minecraft Transport Simulator, which fixed Propeller Bench's crashing issue.