And if something does go wrong, it's less likely to be easy fix.
As far as guns that I think are poorly thought out (not including unforeseen flaws that became apparent after the designing process is already over), I can think of 2. I own one, and used to own the other.
First, the H&R 622 revolver. Sure, it's accurate and all, but in an apparent cost-cutting measure, they designed it so that when you wanna load/unload (instead of being a top-break, or swing-out cylinder, or even a gate-loader) you have to remove the cylinder entirely from the frame to eject spent casings and reload and then reinstall the cylinder. It's a slow, cumbersome, and dirty process that makes even gate-loaders seem convenient and practical.
The second would be the striker-fired Sterling .22 pocket pistol. This is a gun that does not have a slide lock function. When you fire the last round, it cocks the gun and the slide goes into battery as if there was a round chambered. If you don't keep count of how many shots you've fired, you'll end up dry-firing the gun. Yet the gun is NOT dry-fire safe. Furthermore, the gun was not designed with any actual means to de-cock it.