I'd check things in this order;
Barrel floated? (did something get under the barrel in the channel?)
Action screws tight/too tight?
Scope rings and bases tight?
Scope rings and bases tight 2nd time?
Trade scopes to see if that's the problem?
Best of luck and keep us posted.
Sorry I was typing at the same time.
Cheek weld could definitely do that. A trick I've found for that is to turn up the scope so you get a small amount of "tunneling", then make sure to check that the tunnel is centered in the scope. Simple thing but I've caught myself forgetting on more than one occasion and blamed equipment for poor groups then re-shot for groups paying more attention and found that I owed the equipment an apology