Description of the problem is clear, but the details are lacking.
Does the detent on the bayonet mount, not allow it to lie tight, or will it lie tight when oversprung?
Does the bayonet interfere and get blocked from lying tight?
I might also ask, are these the correct bayonets for your SKS?
These rifles have many variants, and parts sometimes get mismatched.
Here is one of the best sites I have found..... target page is bayonet/mounts.
Be sure to page down to the photo and description of 'sag'