When opening a placed autoworkbench the crafting progress bar is already running.
When placing a recipe (say for a furnace) minecraft crashes.

Buildcraft version: 7.99.12
Forge version: forge-14.23.0.2544
Link to crashreport or log (on pastebin or gist, please don't put the entire log here) :
https://pastebin.com/fb2kTQ2g

Singleplayer: yes

What recipe was in the inventory before you placed the furnace recipe? Can you reproduce with just buildcraft?

i just placed the autoworkbench, so there was no initial recipe.
will try to make a setup with only buildcraft.

with only buildcraft the crafting procesbar is not automaticaly running
and it is possible to place a recipe
guess i have to go on a trial and error hunt to find the offending mod :-(
can you find a hint from the crashreport?

found the offending mod:
https://minecraft.curseforge.com/projects/ancient-warfare-2
filed a bugreport there also: P3pp3rF1y/AncientWarfare2#535

sounds like acient warfare is doing something funky with a recipe handler that is claiming to be a valid recipe without anything in the inventory

release 2.4.12 of aw2 seems to fix the wierd autoworkbench behaviour :-)