When you connect energy to the block, it becomes a negative number. The video shows how it happens. BUT i still can craft, looks like its render bug. Also console spams message "[Render thread/ERROR] [io.gi.hw.au.cl.AutoSmithingTableScreen/]: Argument 'toMap' is too big or too small (-31072 > 100000)" Maybe the problem is in the modpack (FTB Stoneblock 3 1.2.3), but it seems to me that it is unlikely.

FTBTeam/FTB-Modpack-Issues#2579
Issue reported on our tracker as well for dw20