Whenever I use the Living Artifact with WX-78, after the timer runs out and he reverts to his normal form, he will no longer be able to eat Gears. The option simply does not appear. I can still examine and use the Gears as crafting materials or as fuel for the Iron Wind, but eating is just a no-no. Relogging seems to fix the issue though.
1. Play as WX-78. 2. Use the Living Artifact to transform into Iron Lord or whatever. 3. After Iron Lord form runs out, there's no option to eat Gears.