Improperly torqued action screws can certainly affect groups. A stripped screw is obviously not properly torqued.
Loose scope mount.
Loose scope rings.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.