Interesting game bug (STALKER: Shadow of Chernobyl)

I tried to somehow get the Dolgovets machine gun that was between the transitions but got a bug. I walk in fragments, that is, I look like 4 steps, then I stop and again I walk 4 steps, then I stop again. Additionally, I am beginning to be damaged by radiation which should not be. How can these problems be solved? I don't want to start the whole game all over again