if not properly maintained/cleaned there is a flaw in the SKS. The firing pin needs to float freely. if it sticks there is a danger of multiple rounds firing.
The SKS is not a knock off. It was designed and fielded before the AK47, but did not have a long run after the AK47 was developed.
Not for nothing, but I believe the SKS is still the most issued rifle in the Chinese military. I am not certain of this - but I know it was the case only a few years ago according to Jane’s Defense periodicals.