For me, I can workbench armor fine and change mods.

But, I can't see anything with weapons. There's messed up letters in the header and no slots. I already lost two mods trying to strengthen my lightsaber.

Does anyone else have this problem?

Is there a solution?

Thx

Not all weapons or armor are modable. That said, you don't actually need workbenches anymore. If an item is modable, you can just Cntl+Right Click on it in your inventory and it'll bring up the mod window.

Give that a try.