Hmm.... that's... this only raises more questions than it answers... I thought the issue might be that the recipe results are defined using the complex {amount = #, name = "", type = ""}, instead of the more simple {"name", amount}, but after Klonan's construction drones mod, it didn't change the recipe at all, so that's not the issue.
I let it run as normal and I was able to get the same error. I then checked the difference between the light armor, like maybe stack_size was undefined before, but it seems the only difference between builds, is that the modified light-armor has a tiny-equipment-grid defined (probably for something used by the construction drones?), but that doesn't seem related to the stack size error at all...
I'll have to research this issue a little further...
EDIT: Wow! It IS related to the equipment grid. Enabling an equipment grid onto the light armor causes the max stack error. And this error would only ever occur when there's a recipe that happens to use an item that happens to have an equipment grid... and light armor just happens to be used by both Robot Army and Construction Drones. It's a very rare circumstance.
I wonder what would be the best way to fix this issue....