I just maxed out reputation with MacCready and got Killshot perc which should give me +20 headshot accuracy but instead it's always 95 even with tiny pistols without range. I checked internet and it seems like a common problem but is there any way to fix it? I think it's a gamebreaking bug and makes the game not challenging anymore.

Bump. Can't even play with this kind of a bug

you could reload a save to before you got the perk and dont talk to macready

I have played 3 hours since then mostly killing mobs in short range in buildings. Only noticed the bug when i got 95 chance to hit the Supermutant on the roof with automatic pistol. I think the only way is to delete the perk with console command. It's strange Bethesda doesn't make a hotfix for this kind of a bug.