It was the lack of instructions from everything I've seen. People didn't know what to do with the small pin in the kit so the simply didn't install it. The kit won't function properly without it. Once they found out where the pin went and installed it, their pistols started working properly again.
The GG pin needs to be installed in the sear in place of the factory pin which is slightly shorter.
I've been following this topic closely on multiple forums. This is the only issue I've read about.
I have the kit installed and am very impressed.