Product: The Sims 4 Platform:Mac Which language are you playing the game in? English How often does the bug occur? Every time (100%) What is your current game version number? 1.63.134.1220 Wh...
As others have said, it's not a bug. The tooltip is just confusing, but it works the same way as the other upgrades in the game. The tooltip is telling you how many parts you're missing. So if it says 2 parts, you're still missing 2 parts.