ZX Spectrum +2 shipped with transistors backwards: https://www.bitwrangler.uk/2022/07/23/zx-spectrum-2-video-fi... This even caused visible artifacts on the display, which was apparently not enough for the problem to be noticed at the factory.
I think Clive Sinclair was notorious for wanting products to be brought to market quickly, with pretty aggressive feature sets. They very well may have noticed it at the factory, but didn't want to do a fix because it was technically functional.