When you have exactly the right materials to make a lamp (two iron plates and three copper plates) and nothing extra (so no copper cables), you are unable to hand-craft a lamp. It cites that you do not have enough ingredients. If you craft the electronic circuit needed for the lamp from those materials first, you will now be able to craft the lamp.
Furthermore, and probably related, if you have exactly the right amount of iron and copper plates to craft multiple lamps (and again, no spare copper cables or circuits) the game will count by two's. So if you have, for example, eight iron plates and twelve copper plates, the game will (correctly) show that you can craft four lamps. However, if you craft just one lamp, the game now shows that you can craft only two lamps. Despite that, you'll still have the resources for exactly three lamps. If you craft another lamp, the game will do so and will continue to show you can craft two lamps. Upon crafting yet one more lamp, it will now show you can craft none, though as above, you have the resources for one more.
Reproduction steps:
[list=]
[*]With lamp technology researched, have in your inventory exactly the following: 8 Iron plates and 12 Copper plates
[*]Observe that, in the hand crafting menu, it is indicated you can craft 4 lamps.
[*]Hand craft 1 lamp.
[*]Observe that, in the hand crafting menu, it is indicated you can craft 2 lamps.
[*]Observe that you have 6 Iron plates and 9 Copper plates (just enough for 3 lamps).
[*]Hand craft 1 lamp.
[*]Observe that, in the hand crafting menu, it is still indicated you can craft 2 lamps.
[*]Observe that you have 4 Iron plates and 6 Copper plates (just enough for 2 lamps).
[*]Hand craft 1 lamp.
[*]Observe that, in the hand crafting menu, it is indicated you cannot craft any lamps.
[*]Observe that you have 2 Iron plates and 3 Copper plates (just enough for 1 lamp).
[*]Observe that you cannot hand craft any more lamps like this.
[*]Hand craft 1 electronic circuit.
[*]Observe that, in the hand crafting menu, it is indicated you can craft 1 lamp.
[/list]
Expected behavior:
That math is done right (I'm guessing this is a rounding error).[\strike]
