tl;dr EPOE workbenches don't detect stacks of prosthetics, they only detect prosthetics if they're placed down separately.

I found out I have a stack of 200+ light receptors, and that my workbench says "2/4" light receptors made. To test it out further, I started a new game and placed 5 receptors down separately, and spawned 2 of those stacks with multiples. I looked at a simple bionics workbench and it still shows only 5/1 made, ignoring the stacks on top of them.

The trade screen still detects the stack of prosthetics though, so that's not an issue.

So ya idk what to do with this.

edit note: my stack XXL is set to like x200 each stack, with body parts toggled on.