I was using a diamond wand to make a platform of stone bricks. A nearby essentia smelter (with smelter vents) was above me. When I looked up at the smelter, with the wand in hand, the game crashed with the following log: https://pastebin.com/gcqJ0a3q

Also reported on the Thaumcraft 6 github: Azanor/thaumcraft-beta#217