There must be "space" in the chassis that allows it to walk out.. May need to fill / shim the chassis for a more snug fit.. What is the chassis? Aftermarket something or factory Ruger..Here...finished taking the rifle apart... Pic
As you can see, the trigger pin has walked out of THE hole in the housing... And thereby, it will not shoot semi... You have to re rack the bolt every time to get it to fire...
Just thinking... It always walks out of the hole on the left side of trigger housing also...