Knowing Kel-Tec they probably run fine once you go in and polish everything and work the bugs out. A lot of people have trouble with KSGs. I think the early generations had some bugs. A lot of people do what they call a "Fluff and Buff". There are detailed instructions how to do this available on the KSG forum. I never had to do any of that. At some point around 1000 rounds I started noticing while I was cycling it ( Not shooting, just running the shells through it) I was having some FTF. First I considered the fluff and buff thing, but it occurred to me that was probably not an issue that would magically appear after 1000 rounds. Turns out I was right and the issue was the design of the selector switch. The screw that holds it in place can't be torqued, because the switch needs to move. So rather than using a shoulder screw they just used a flat screw which you cannot fully tighten and mine had loosened up. So I took it apart, cleaned it thoroughly, then put some blue loctite on the threads and tightened it fully then backed it off until the switch operated freely. No more problems.
I think most people's problem though was that they simply didn't/don't know how to run the thing. A very popular saying is " Rack it like you hate it". Which is one of the stupidest things I've ever heard. If I had to slam a shotgun to get it to feed I wouldn't have it for long. Mine feeds and ejects perfectly regardless of the speed or force with which I charge it. The trick is that you have to actually pump it the entire length of it's travel, BOTH directions. All the action happens in the last 1/2" of travel on either end. So people short stroke it.
See, bugs. I'm under no illusion that my KSG is some top shelf shotgun, but mine runs like a clock. The trick is to be smarter than the shotgun. The Israeli shotgun is definitely a much more well thought out design. 16 rds. in 8 seconds and you don't need to do anything but clean it. And some dude I saw ran his over 600 rounds without doing that before it got stupid. Then he just cleaned the gas piston and started shooting the crap out of it again. Anyway....