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.

The +2 was an Amstrad product, not designed or built by Sinclair, though.

Didnt at least some engineers transfer after acquisition?

Maybe. I don't think a lot did. Amstrad did not acquire the company: it bought some rights to use the Sinclair Research brand.

That's why the next computer Sir Clive launched was the Cambridge Computers Z88. But note, some of the later bicycles were Sinclair Research branded:

https://en.wikipedia.org/wiki/Sinclair_Zike

https://en.wikipedia.org/wiki/A-bike

Amstrad did not acquire or develop the Sinclair QL, for instance, but it did sell Sinclair-branded x86 PCs.

https://www.computinghistory.org.uk/det/3404/sinclair-pc200/

It sold on some stock of existing ZX Spectrum hardware, but mostly it sold models it developed:

* Spectrum +2 -- a Spectrum 128 with a mechanical keyboard and built-in cassette drive

* Spectrum +3 -- a redesigned Spectrum 128 with a DOS from Locomotive Software and a 3" (not 3.5") floppy drive. Dropped compatibility with 48 peripherals such as Interface 1 and Microdrives, and 128 peripherals such as the numeric keypad, serial ports, etc. Added the ability to page out the ROM and replace it with RAM, so it could run CP/M 3, also ported by Locomotive.

* Spectrum +2A, the black +2: a cut-down +3 with a cassette drive.

These were designed by Amstrad engineers and contractors, and manufactured by Amstrad. No Sinclair involvement I'm aware of at all.

Commodore just kept doing this. Just listing shoddy craftsmanship would take forever, and then we get to intentional bad decisions, like giving the A1200 a power supply that's both defective (capacitors ofc) and barely enough to support the basic configuration with no expansions, which is extra funny because PSUs used with weaker models (A500) had greater output...

The number of used a500 power supplies I sold to customers when I upgraded their a1200 with a GVP 030 board + RAM...

This was the hardware patch I had to install to use a CyberstormPPC: https://powerup.amigaworld.de/index.php?lang=en&page=29

Classic Commodore Quality :P

They also had backwards caps on the CD32 and A4000